Allow me to start with a brief description of my 6-year marriage.
We were both young then, both 20 years old. We had the perfect Girlfriend/Boyfriend relationship back then and we met at the office. About 6 months into the relationship, we got pregnant and got married shortly thereafter (mostly due to her parents wanting us to get married because of the baby - a standard Philippine Custom...).
While that wasn't a good start to begin with, we managed to grow our love on the first, say, 5 years of our marriage. We went through a lot of problems, like Sex (or the lack of), family, finances etc, and we were able to get through them all.. together...
Time flew by and before we know it, we both got a stable job, rented our own apartment for a while and our kid grew to love everyone around her. It was perfect, I am holding a Corporate-Management level employment at age 26, and she is also slowly climbing the ladder of success as a Supervisor-level.
Then we moved into my in-laws place (we both agreed), primarily because we now have a brand-new car we need to pay off, and after that, our plan is to get a house and live our happy life as a family, all within the goals I set for my life (at 30, I want to be paying my own house).
In her new work (we still work in the same company, my office is barely 20 steps away from her desk), and I have realized that she has been going out too much. She has been keeping her cell phone away from me (on silent - non vibrate mode), and deleting "selected" messages consistently. She rarely invites me to lunch, knowing that I eat and smoke alone most of the time... I invite her for a date, she doesn't want to and would always want our daughter to be with us...
We spoke about this too many times, for I felt she was hiding something (who would delete "some" messages and recent contacts entry if there is nothing to hide?) All reason she said was, it was none of my business, and she in her friends (guys) have their own secrets because they found a confidant in her. She has been regularly been going drinking with officemates (twice a month), and goes home at 9AM after the previous night's drinking and party session. We spoke about it far too many times, that I do not like that, it hurts me, it insults me.. blah blah blah... Nothing... She also doesn't want me to go out with her and her friends, her reason being her friends are intimidated by me because I am a "Boss" at the office.
It seems that she does not want to change.. Yet... And she told me she wants to experience things she didn't get to experience because our marriage was too early... She wants to experience going out, having friends, partying, going to the beach... All without me...
I feel so insecure, so depressed, thinking that she might be seeing or becoming emotionally attached so someone else... I know exactly what she is doing now, because I did it myself quite a few times, even to the extent of having a sexual affair with quite a lot of other women during our marriage (but that is long over now).
She said she loves me still, and ask me not to worry (I trust and believe her when she says this). Because at the end of the day, I am her husband and she will always come home to me... But the instinct in me is telling me something is going on, or something might happen (I know men take advantage, coz I did too)
The ladies in their family has always been the dominant type, and I for one is also dominant, and have the always-right-wont-loose-a-fight type of guy which could not be a healthy mix at all. (We both laughed about this once, since this is what brings spice to our marriage)
What should I do? Should I trust and let her discover her "single" side? I gave up on all the arguments as it doesn't seem to change at all... I have been a good provider, father and a sweet and loving husband (small, random surprises, hugs, kisses, tell her she is gorgeous, name it, that is me)... But what makes her want to be with them.. and not with me?

I'm just too afraid that she will realize its better out there without me...
I miss the times that I was her everything, when I was at the top of the list, and it hurts being in second, sometimes third place... This has been going on for the past 3 months, and it is taking its toll on me and I am starting to feel the symptoms of depression...
Any advise would be greatly appreciated. Cheers!