Weird thing my bf does during sex😅

Okay ladies!🚺 So, my boyfriend does this "weird/interesting" thing during sex and I want to know if any of you gals have experienced this as well.

During sex, whether oral or vaginal, my boyfriend has a tendency to stick his middle finger in my butt while he's eating me out or during penetration. Being that we've just recently started having sex and that he is my first, I am very much inexperienced and though I like the feeling of when he does it, it's still kinda weird and new to me.

Anyone experienced this too?