My boyfriend has already told me he loves me, but he still loves his ex, I don't want to stand in the way of his happiness, what do I do?

Many will always have some "feelings" for their ex. How soon after he broke up with his ex did he get with you ?

Perhaps you should part for a while and let him decide where his feelings are.

Talk to him and ask him if he really feels it would be good for the two of you to be in a relationship right now. If he doesn't think he can handle it, then don't be his girlfriend, and don't let him flip flop between the two of you because he can't choose. You are friends until he decides, unless he decides or knows that he wants to be ONLY with you, and that he can control his feelings for his ex.