I can't comment on your relationship, whether you should fight for him or not - but let me tell you my story as a cautionary tale.
I married in my 20's, my husband had some ambivalence when we married, he cheated on me early in the first year. I took him back, forgave him, thought we had gotten through it. WE had three kids, a good life together - really, 90% of our marriage was great, we were the couple people envied.
But - long story short, my H had never really dealt with his issues. And they slowly poisoned our marriage. He had another affair when our kids were teens, I forgave him again, we had a few more good years - then he walked out as he approached 50. WE are now divorced after 25 years of marriage, I'm a 54 year old woman trying to negotiate the dating scene.
And I can see in retrospect, that I spent a lot of energy over the years trying to placate him and keep him happy, trying to hold onto him, not feeling truly cherished and valued for who I was.
I had three kids and a lot of reasons to try to make it work. I don't regret that. But if I could have known when I was your age what the future held? I would have run. I would have realized I was settling because some part of me didn't believe I would find someone who adored me the way I adored my husband.
Your husband has shown you his character. Yes, it sounds like you could have handled things better - no man likes a nag. BUT - you know that you were reacting that way because he was NOT giving you the love and reassurance that would have been required for you to get over his previous infidelities.
I know it hurts, but I believe this kind of situation is different than the rest. Don't try to get him back. You don't want him back unless he can REALLY change, and can PROVE he has changed for a prolonged period of time. You don't have kids with him yet - think long and hard whether this is the character of a man you want to be the father of your children? Focus on your own growth and don't dream of taking him back unless he attends 6 months minimum of counseling with you and is completely transparent in all his activities.
And - sorry to suggest this - but be prepared for the possibility that he has been cheating. I've seen a lot of cases here, when the H bails right after the wedding, and it turns out they were cheating before the wedding but just didn't feel they could stop the train.
