I've been experiencing on and off bouts of constipation and diarrhea. also intestinal cramps. family history of celiac disease. e.r md thinks gerd?

Gluten bad: Gluten sensitivity genes are inherited. If celiac runs in your family, you likely have a gene or two. Not everyone will test positive. Do yourself a favor and do a trial of gluten and dairy free diet for a few months and see how you feel.

Many possibilities.: GERD doesn't explain it. Constipation can though. Sometimes if you are constipated you get so backed up that eventually it comes out forcefully and fast (i.e. like diarrhea). If you stay regular it could go away (prune or pear juice, senna, docusate, miralax (polyethylene glycol) -- all over the counter). Take even if you start going to make sure it doesn't build up again.