GRAPHIC POST! Urge to Poop in Missionary and Doggy Style???

Has anyone ever experienced this? Whenever my SO and I have sex in missionary or doggy style positions, I always get the urge to poop because I feel like his thrusts are hitting my rectum. I never experience this from the side or while lying on my belly. HELP PLEASE!!!! My guy loves doggy style but I hate it since I can't focus because I feel like I'm gonna shit myself.