Is it normal that i don't love my girlfriend?

Okay so I used to be really in love with this girl who likes me as a really good friend. Shes aware of how I felt but never had a sexual attraction to me although she gave me a chance we made out and stuff but nothing. She had an ex boyfriend who went to the Marines and broke up with her then had sex with her bestfriend. Hes out of the Marines now but hes a totally different guy now and she doesn't know how she feels about him anymore. While I was in love with her my friend was in love with me. Shes really head over heels for me so much that she used to endure me talking about how much I loved the other girl just so I would be talking to her. I was aware of how she felt but hoped she got over me because I don't like her as anything more than my bestfriend. I decided to go out with her a couple months ago since we were talking all day all night I wanted to give her a chance. Shes awesome together we have the same tastes, shes attractive, shes funny and best of all shes faithful. Although after all of this I don't "love" her like I did my first love mentioned earlier. I don't think I will love any girl like I did my first love but this girl is really good too. I don't want to leave her like my first love left me so right now i'm enduring her love but I know for sure I don't feel the same way she does. Shes my bestfriend so its not hard to pretend that I do but honestly its starting to hurt me that if my first love was to say she suddenly loves me and wants to go out with me... I don't know what i'd do. I know i'm supposed to say no because its to late but I don't know if I could. I love her to much but my new girlfriend is amazing. EVERYONE says me and my first love act just alike and haha I saw it since the day I met her. Me and my new girlfriend are great together as well though just like my first love.