I sit on my dads lap and i am 18.?

-I like to sit on my dads lap and i am 18 girl. When ever i sit on his lap i can feel his pen*is getting harder. When he gets a full erec*tion i move a little to get his pen*is in between my a*ss cheeks. I think this is very hot and sexy. It is also very comfortable i my dad probably like it because he doesn't move that much when ever he has an erect*ion. One time i sat on his lap and i had on a short shorts ( i even rolled them up so they really only covered my a*ss) and of course a shirt on. When i went on his lap my skirt feel forwards a little so half my a*ss was hanging out. I had on a g-string so he could see that when it feel forwards. He had on shorts and a top. That time he got an erect*ion twice as fast it felt like.It also felt more detail to i could even tell about the size of his pen*is. It has never gone farther then that. Does anyone else have this happen to them.