Girlfriend frustrating me

I have been dating my girlfriend for about 8 months. I told her I loved her for the first time about two weeks ago. For the first two months we fooled around a few times per week but for the rest we only fooled around about once a week (we're not having sex). Since then, we have not done anything physical but kissing. Our relationship in every other aspect seems great but I can't seem to get her interested in being physical again. Why might she be less interested in being physical and how can I get her interested again?

She's interested in someone else. You're boring her. For the first year it should be mindblowing. Then its a gradual decline however you put it. It doesn't have to be but for most people it is.