I need advice ..

So I’m currently 6months pregnant the pregnancy was not planned and and when I found out my current boyfriend and I had only been dating for three months .. I had feelings for him and now I feel myself starting not to be interested in him I want to tell him how I feel but I know it’s just going to devastate him and that’s one thing I don’t want to do .. he such a good guy but I don’t feel like we are meant to be together.. I want him to be in his son life but I just don’t want to be with him and me not be happy for the sake of my child I feel like if I do that it’s not going to be good for my son , idk what to do I have so much mixed feelings about this .