I feel stuck

Ladies I just don't know what I'm doing anymore. I'm 20 years old with a 1 1/2 year old daughter whom I love more than life it's self. I'm currently engaged to her father. We have been together for 4 years. I just don't feel like I'm in love with her father anymore. Our sex life is still really good. We talk, laugh, and smile with each other just something is feeling off to me. It's like I find myself laughing till I have tears in my eyes with him and then the next moment I just look at him and I just don't feel it anymore. He is such a great guy he does everything for our daughter and I. I just want to love him the way he loves our daughter and I and it hurts a lot. I finding myself crying because I just want to love him and be happy with our little family.