He stopped saying i love you.

So we aren't in a relatiionship but have always had feelings for each other and been very open about it. It has been six years now. Lately when i say i love him he just says thanks. He's been talking about wanting us to be together for almost a year now and suddenly hes changing. We havent got together because things are rocky. He lives at home and we arent out of the talking about it stage. We fool around like 2 times a year. Last may i got pregnant and he was supportive in whatever i chose.. But then i lost it. Recently we had a scare but turns out im not. I know he wants a family some day but i feel that its not for me. Its another reason why i havent been able to commit. But im confused.. I think i would do it for him. Right now i just dont know how to react. He wont say it back and is asking if im sure that i love him. I only get a thanks.... Not sure if i should just back away or what..