He feels something poking him?

Ariel
So I don't know if it's related to how turned on or "ready" I am or what, but sometimes when we have sex my guy feels something poking him and we have to stop. Its really frustrating. Could this have to do with not enough foreplay or something? I read that vaginas stretch easier based on blood flow and arousal, so could he be hitting my cervix if I'm not aroused enough?