I don't enjoy the time we spend with my husband's friends. He accepts that but I know it hurts him.
The issue is that they disliked me during the dating years, and showed it with pretty bad behavior - e.g., not talking to me at social events, anger at my husband for spending time at my family function instead of with them, etc. My husband was a longtime single and very social guy. We met a little older, and I think they resented his not being around 100 percent any more.
Anyway, as time progressed, years, and they realized the permanence of our relationship, I guess they decided they had to be my friend or lose him.
My husband wants me to brush it all aside and be friends. The problem is that, even if I understand and even forgive them, I still feel self-conscious, and clam up because I feel they are only putting up with me because they have to.
I am already an introverted person, and spending time with them exhausts me because it brings my anxiety level way up. I've suggested he spend more time with them without me, but he says he wants to spend time with us all together. He does spend a lot of time with my family and friends, but they love him and always have.
Answer: The best thing you can do for you is to let this old grudge go. The years have likely matured you all, so the friends' behavior needn't define them always.
Also: It sounds as if you're taking very personally something that wasn't entirely about you. Your then-single husband was the guy they could count on, not just in those big communal years right after college, but also years into the phase where people start disappearing into their own little orbits.
So his friends' resistance appears to have been not to you specifically, but to his pairing off in general. The life of their party went home.
Maybe you also need to stop blaming yourself for being the one who took the life of the party home. That wasn't your decision, that was your husband's. He's still very social and wants you to be, too.
His friends, apparently, are OK with that now. Why not see what happens if you decide to be OK with it, too?
Your introversion is best dealt with as separate from your bad start with these friends. When intro- marries extro-, that demands adjustments and compromises. He is energized by others, and you are drained by them. So, he needs more nights out than you do, and you need more nights in than he does. Make plans accordingly, and talk openly of keeping each other's needs in mind versus trying to bring each other around to your way.