My gf is obsessed with anal.

I 18M and my 19GF have been together for like forever. We've known each other since we were kids and started "dating" in primary school but made it official official in high school. Our love life has been nothing but amazing. There's nothing wrong with our relationship. It's just that when we tried "anal" about 2 and a half months ago, she, as been obsessed with it, honestly, I have nothing wrong with that. I just I don't know feel like we are doing anal too often. "we do it 3 times out of 4 times a week sometime," and I just don't know how to tell her. I know I must look dumb and all, but I just need a little help it would be much appreciated, thank you.