breakup

I just started seeing this guy and I do really like him he was my best friend before we started dating we haven't been seeing eachother very long but I don't really think I want to be with him anymore I mean he makes me happy but I just don't think I have those type of feelings for him I have no clue how to tell him about this he was so upset and in a bad place before we got together he's been so much happier I don't want him to go back to that but all I do is think about other people I've been with I don't want to hurt him or lead him on how should I end things without him falling back into a depression