Please help kind of embarrasing?

so i was with this girl last night. and we went to the back room and did stuff. It was like my first time ver doing stuff with a girl. we did everything but sex. well durring this IDK why i couldnt get a full ***** like it just wouldn't go idk why cuz i thought it was pretty G doin stuff. but i just couldnt. yet when i watch porn though its like a sky rocket. so what is wrong please help