Well. let me explain a little bit where I'm coming from:
I was married for 24 years. My ex cheated on me in the first year of our marriage. I forgave him, took him back. We went on to have a largely good marriage and three kids.
Then when the kids were in their teens, he cheated on me again. Through the lessons I learned on this board, I was able to save our marriage at that time; in fact, we went on to have several more excellent years - until he approached 50 and went into full midlife crisis. I was unable to save the marriage that time and am now divorced in my 50's.
It was very traumatic for my children. And what I realized was, when I took my husband back the first time, I knew I was taking a risk - but didn't realize that I was also taking a BIG risk that my CHILDREN would have to pay for.
There were "red flags" about my husband's behavior from the beginning - I just chose to ignore them. I wish I hadn't. (And to be honest, it sounds like my ex and I were much better matched in terms of goals than you and your BF).
So, my advice to young unmarried people who come here is: this is not a situation that calls for "standing" very often. Your BF is showing you what he's made of. If you DO take him back at some point, DON'T do it too easily - make him see a counselor and do the work and prove himself to you.
Imagine yourself ten years from now, perhaps with a child with a serious illness or disability - is your BF really the kind of person you could count on when things get difficult?
(Oh - and in case you are wondering - I've been divorced now for five years. When my ex left I learned to play the drums and now play in two bands. I have a thriving business of my own, a nice new house, and a tall dark and handsome boyfriend who treats me like a queen. )
)