I have a problem. Please help.

I'm afraid I don't have any more feelings for my boyfriend. We've been together for 3 years now, He moved to Germany from Italy for me. I don't feel the love I felt for him before, but just a big affection. I don't want to lose him in my life, but I feel like I'm doing him wrong by not telling him the truth. He's a very sensitive guy, he has a lot of self-esteem issues and I don't know how to even start this conversation with him.