She often seems unstable.
JPP, the two most common causes of emotional instability are a strong hormone change (e.g., pregnancy or postpartum) and drug abuse. If you can rule those out -- and you've not yet mentioned them as problems -- the two remaining common causes are BPD (Borderline Personality Disorder) and bipolar disorder. I therefore suggest that you familiarize yourself with the warning signs for both BPD and bipolar. Below, I will focus on those for BPD because (a) it is much more common, (b) you seem to be describing BPD red flags, and (c) even if your fiance had exhibited bipolar behavior in the past year, that would mean she has a 50% chance of also having BPD.
The behaviors you describe -- i.e., irrational anger, controlling behavior, easily triggered temper tantrums, black-white thinking, verbal abuse, and always being "The Victim" -- are some of the classic warning signs for BPD. Importantly, I'm not suggesting your fiance has full-blown BPD but, rather, that she may exhibit moderate to strong traits of it. I also caution that BPD is not something -- like chickenpox -- that a person either "has" or "doesn't have." Instead, it is a spectrum disorder, which means every adult on the planet occasionally exhibits all BPD traits to some degree (albeit at a low level if the person is healthy).
At issue, then, is not whether your fiance exhibits BPD traits. Of course she does. We all do. Rather, at issue is whether she exhibits those traits at a strong and persistent level (i.e., is on the upper end of the BPD spectrum). Not having met her, I cannot answer that question.
I nonetheless believe you can spot any strong BPD warning signs that are present if you take a little time to learn which behaviors are on the list. They are easy to spot -- especially after you've been living together for six years -- because there is nothing subtle about behaviors such as always being "The Victim," lack of impulse control, and rapid event-triggered mood flips.
Me and my fiance have been together almost 6 years now and the last several have been a constant string of fights, resentment, and distrust.
If your fiance really is a BPDer (i.e., exhibits strong and persistent BPD symptoms), it is highly unlikely you would have seen those symptoms only in the last three years. A BPDer typically is symptom-free only during the infatuation period because the infatuation convinces her that you are the nearly perfect man who has arrived to rescue her from unhappiness. In that way, the infatuation holds her two fears -- abandonment and engulfment -- at bay.
When the infatuation starts to evaporate, however, those two fears return and you will start triggering them. Indeed, it will be impossible for you to avoid triggering them. Hence, because the infatuation starts waning about six months -- perhaps even a year -- into the relationship, you should have seen her distrust and anger starting to show by the end of the first year. Granted, it is possible that the infatuation lasted two years but that is an unusual situation. I mention this because, if you really did see these issues occurring only after 3 years, I would be skeptical that you are describing a persistent pattern of BPD symptoms.
We have sought counseling and while it helped in the short term nothing really changed.
If she is a BPDer or bipolar sufferer, marriage counseling likely will be a total waste of time until that underlying issue is treated in independent counseling. Although MCs usually are excellent at teaching communication skills, a person suffering from BPD and/or bipolar has issues that are far more serious.
She suffers from depression and anxiety.
If your finance is a BPDer, that is to be expected. A 2008 study of nearly 35,000 American adults found that about 80% of the female BPDers suffer from a co-occurring mood disorder such as depression and anxiety. Although medication cannnot make a dent in BPD behaviors, meds nonetheless are prescribed to BPDers to alleviate those co-occurring depression and anxiety disorders.
She does not work, spends her days in either a manic state where she cleans the house and everything else or in a depressive state where she sleeps all day and ignores the world.
If you are referring to an actual manic state, you are describing a warning sign for bipolar-1 disorder. People having that disorder experience moods swings between a manic state and a depressed state. If the mania is very mild, the disorder is said to be bipolar-2.
If you bother her she flys off the handle in a fit of rage.
These event-triggered rages are one of the hallmarks of BPD. Because a BPDer carries enormous hurt and anger inside from childhood, you don't have to do a thing to CREATE the anger. Rather, you only have to say or do some minor thing that TRIGGERS the anger that is already there. This is why a BPDer can burst into a temper tantrum in ten seconds. In contrast, bipolar mood changes typically take a week or two to develop and even longer to disappear.
I feel and I can see that our daughter feels like we're walking on egg shells around the house to not upset her.
If you and your daughter are living with a BPDer, "walking on eggshells" is exactly how you should be feeling. That's why the best-selling BPD book (targeted to the abused family members) is titled, Stop Walking on Eggshells
I'm the bad guy.... it's always my fault.
Again, if you're living with a BPDer, being blamed for every misfortune is exactly what you should expect. BPDers have very fragile, unstable egos and therefore don't have a strong sense of who they are. To the extent that a BPDer has any lasting self image at all, it is the false self identity of being "The Victim" -- always "The Victim." A BPDer therefore keeps a death grip on that false self image by frequently "validating" it by blaming the spouse for every mistake and every misfortune.
Should I read more books and articles about depression and anxiety?
My advice is that you read, instead, about BPD and bipolar warning signs to see if most sound very familiar. And, because you have a daughter with this woman, I suggest you see a psychologist -- for a visit or two all by yourself -- to obtain a candid professional opinion on what it is you and your daughter are dealing with. This is important to know because, if your fiance really does have BPD or bipolar, there is some risk (perhaps 15% to 30%) that it could be passed on to your daughter. If your D is at risk, BPD symptoms likely would not be evident until the early teens and bipolar onset typically occurs in the mid-twenties.
When BPD is a strong possibility, it is important to consult with a psychologist who has never treated or seen your W. In that way, you are assured that he is ethically bound to protect YOUR best interests, not hers. I also suggest that, while you're looking for a good psych, you read my description of the major differences I've seen between the behaviors of bipolar sufferers (e.g., my foster son) and BPDers (e.g., my exW) at 12 Bipolar/BPD Differences
If most of those BPD symptoms sound very familiar, I would suggest you also read my list of 18 BPD Warning Signs
and my more detailed description of them in Maybe's Thread
. If that description rings many bells, I would be glad to join Farsidejunky and the other respondents in discussing them with you. Take care, JPP.