How on earth can he stop you from leaving?! If you want to leave, leave. It is not up to him. That is *your* decision.
You have to decide what you want for yourself: you either choose to stay with a husband you *know* will keep cheating (as his actions keep proving to you) and make peace with that OR you show yourself AND YOUR KIDS the self-respect you deserve and leave.
Children are not happier when mom-dad stay together at all costs. What you are actually teaching them by staying is that it is okay for daddy to cheat and disrespect mom. Your daughter(s) will learn that it is acceptable for their husbands to cheat on them and they should just accept it & your son(s) will learn that it is okay to cheat on their wives and disrespect them. Is that the example you want to leave your kids?