While there is always some small statistical chance of being pregnant, it would seem that's been pretty certainly ruled out. Put that alongside the fact that your symptoms certainly don't seem gynecologically-related and it seems even more unlikley. Not impossible, but unlikely.
Meanwhile, you do sounds like you have a gastrointestinal problem of some sort, and it could be as simple as irritable bowel syndrome (IBS) or as obscure as celiac disease (which can cause symtpoms similar to what you describe, but is caused by gluten intolerence, a dietary issue). Since it would seem you've been somewhat concerned about a possible unwanted or at least unplanned pregnancy then IBS is a possibility since it is often aggravated or initiated by emotional stress. If the problem continues there are ways of treating your symptoms, but you should be examined and have both IBS and celiac disease ruled in/out, as well as anything more serious which might be causing the symptoms. I'd put my money on IBS first, celiac disease second, but there's only one way to be certain and that is to have the appropriate workup and see what, if anything, is going on. Again, pregnancy seems like a pretty distant likelihood.
I hope this is helpful. Best of luck to you.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist