Triggering the need to poop

Sorry for the gross topic, but I need advice. I have a helix Syn and a Progasm. When I use either one, it keeps triggering the need to poop. I always go before a session, but it never fails that I have to stop my session at least once or twice to have to poop, not to mention make a mess. Last night it was three times and I finally abandoned my session.

I have tried a bulb cleaning before as well as upped my Metamucil.

Any advice is appreciated.