Well, I never feel great when I'm constitipated, but if it's too the point of intense intestinal pain, I'd be inclinded to not ride. I got the sense from the OP that she was more concerned about having to make an emergency pit stop during a ride.

As for your situation, westtexas, I'd be inclined to talk to my doc. To go from chronic constipation to the opposite end of the spectrum isn't entirely normal. In the meantime, you might try taking fiber supplements. Believe it or not, extra fiber can firm up your stools, too.