Weird symptoms?

Okay so I've been having this odd stomach stuff going on that I read somewhere could coincide with pregnancy symptoms. I will have awful gas, diarrhea, then constipation. My stomach will hurt so bad I can't even eat or go to sleep. I went to the doctor's today & my doctor asked if I could be pregnant? Can someone please explain as to why he would think that? I'm worried I might be now, but it just doesn't make sense. Someone please enlighten me