Has this ever happened to you and your SO?

I've been dating my boyfriend for the past 5 months. He lives about 4 hours away so we usually see each other on the weekends (Fri-Mon). Either I go to his house or he comes to mine. Basically we've realized that almost every time (90% of the time) we're together neither of us can poop. It's not that we're uncomfortable around each other, we just physically can't.

At first I thought it was because of the diet change when we go to each other's house, but it happens even when I'm at my own house (when he comes over). And the weirdest part is the second I leave or he leaves we both have to poop. Both of us think it's funny but sometimes we get worried when we hangout for longer periods of time.

Has this ever happened to you and your SO? What do you think is causing this?