Why don't i feel anything when my girlfriend kisses me?

So, I've been dating this girl for a year and I love her to death. When I think about losing her or having her not with me it makes me feel horrible. When I look at her and hold her I feel attracted to her, I get excited thinking about kissing her... but once it happens I feel not really anything special. Just lips touching other lips. When she kisses or bites my neck I don't feel anything either, and it makes frustrated because I know when I do the same to her she definitely reacts to it.

There's a lot more i could probably say here but if I did I'd be writing a goddamn book lol. So... is this normal? Am I in denial? Is she just bad at it? Please give me your thoughts on this.