K.B.
Its difficult to gain trust back after something so devastating has happened. I also tried what you did and really had hoped it would work out but I wasn't able to trust him again and he was up to his old habits. He had left for another woman. I took him back hoping that things would work for my daugther's sake. I think I thought I could do it despite the odds that it wouldn't work out. One thing I wish I would have done before I ended it was to get really good counseling. I think its worth it to see a marriage counselor a few times before you really decide. If you "can't afford it" like I felt I couldn't at the time, think again. You have no idea how expensive lawyers fees can be so you may be saving money in the long run. This really isn't something you can just "get over" and get on with your life as if nothing happened. He broke your trust, he put you into a tailspin and you're supposed to pretend like nothing happened? This is really something a seasoned marriage therapist should help you with.
If you decide it just isn't working and you've tried everything then you can move forward with divorce. You will get child support and I believe you can figure out how much that will be if you need to budget. I can tell you this, being a single mom can be really difficult and you have to think about the fact that your kids will be away from you for a minimum of every other weekend and one night every week. He will always be their father and you will always have to deal with him as such and work out the details of your kids lives. Your kids will have to get used to being shuffled back and forth and probably even have to deal with stepparents at some point.
Its a tough road and its not a decision to take lightly.
Sometimes it is what is best for everyone involved but other times the hard work of rekindling a marriage can be worth it. Do the work first, then decide.
From a divorced single mom who's "been there."