What do I do?

I have been in a realtionship for over a year and a half now. Too save all the details we are very much in love and everyone around sees it also. 
Two months ago he broke up with me then cried at my door saying how he made a mistake and begged for my forgiveness(3 weeks after the break up)
before the break up he was acting different he had new friends and was a different person, he still is now.
Sometimes I'm with him and he's the same amazing caring person I fell in love with and other times I question who he is.
I'm stuck in the middle, what do I do? 
I don't want to bring it up as I'm scared he will brake up with me again and I can't imagine anything worse.
Please help me.