Your relationship does not sound very loving or trusting, which are two things that you really need from the father of your children, not to mention from someone that you would commit yourself to or do anything for.
You are 16, which is kinda young to be in such a serious relationship. It's been done before, of course, but this doesn't sound very healthy. Find someone who values you and your feelings! Someone who loves you should not be sleeping with other people unless you've agreed to an open relationship, and should also be openly communicating with you, which he is obviously not.
My best advice would be to break it off with this guy and find someone who truly cherishes you through his actions, not just his words.