Ladies: Why does she do this in bed? (re-post)?

I like to perform oral on my gf, I even like to pretend I'm making out with her p***y, nice, slow and sensual (I am very careful as well). However lately she has turned me away from it, we still have and everything. I know she likes it when I am performing because she moans and twists....But why would she turned me away now when she loved receiving it before?