Hi Red, ok I will give you my advice on what I think will help you, please again I am NO expert, I will just tell it to you as I see it. First, sit down with your husband when you have time together alone, no tv, kids, etc. Tell your husband exactly what you said above word for word, that you did not want to do the things he talked you into to doing and that you regret doing it and feel hurt and resentment towards him. Make sure that you say EVERYTHING that you feel and think about it, don't leave anything unsaid, be specific.
Then tell him (I think this is what you are indicating if not I stand corrected) tell your husband that you do not want to do anything like that ever again, and then forgive him for what happened. Hard to do, but make a DECISION to let it go. Neither of you can change what happened, but you can change today and every moment forward. I also suggest, if you are willing, to decide on a time each week to discuss difficult issues, what is bothering you both, hurting each of you, what things you can each do to improve your marriage, SPECIFICALLY what each of you would like to do in your marriage that each of you may feel is lacking. Confine this type of discussion to once a week for a specific time only. Then at the end of this discussion choose to tell each other at least one thing that happened over the previous week within your marriage that was really encouraging or exciting or helpful. Then, and this is for you Red, because you are the one asking for help, during the rest of the week, when you feel resentment or anger or irritability creeping up STOP, go for a walk, go in the bathroom, if possible ask your husband to excuse you for a time, sit down focus, DECIDE...is what I am about to say going to build up my marriage or tear it down? Then you have to decide, if the answer is tear it down, is it worth it? I have found (in my own life) that some of what we do is habit, we have control over our mouths, our actions, our reactions. It seems that you may be getting into a habit of arguing, CHANGE IT, you can, it may not be easy, but it gets easier as you practice it and the habit can be broken. I was in the habit of saying what I thought and felt before stopping to think of the reaction of others, and surely I do not do it perfectly, but I have found that as I get better at it there is much less strife in my life with others, and I am having more peace in my life. Please understand sometimes you may be VERY justified in saying what you want to say, but stop and think about it, is it really worth it, especially for you if you have made the decision to forgive your husband, then you must really work on letting it go. I believe this is truly why you are arguing, deal with it, let it go, and learn the very very hard task of controlling what you say. If you do decide to try this, I will be interested, if you start having success with it as I have, to hear of the outcome.
OK, now I am going to suggest something that you did not ask about specifically. You indicated that your husband at the outset of his mid-life crisis desired more spice in his sex life. Well that is certainly something you can do that is extremely healthy for your marriage, really fun, and will probably make you feel better also. YOU spice it up, it is easy and I think it is fun. I will give you one example if you already don't do it. Talk to him about it in places that you cannot do it. On the phone when he is at work, right before you are about to enter the family home for Christmas. I am serious, if you have not tried this, do it, you may be very pleasantly surprised
) Looking forward to seeing if you try any of this and if it helps you. Hoping your marriage mends completely and becomes happy for you both!