Seafood allergy?

Ever since returning from a 2 month stay in Mexico last summer, I have been experiencing stomach pain, vomiting and diarrhea in seeming random and unconnected situations. I have been tested many times for different parasites and allergies, I have had small and large bowel follow-throughs and ultrasounds. I am currently waiting to see a GI specialist but I am starting to lose faith in doctors.

Recently, I have connected this nausea with certain seafoods. I can't eat shrimp or salmon but canned tuna doesn't seem to be a problem. It has improved over the last year, but the symptoms have maintained a similar pattern: approximately 2 hours after eating the offending item the stomach cramps start. Then, I usually throw up at least once and this is followed by severe stomach cramps. Then, everything in my digestive tract becomes liquid and I have an hour or so of urgent diarrhea. Usually, it takes several hours before I feel myself again.

After my last bout (brought on by cooked salmon - a new development), I had a couple of bouts of diarrhea and generally I experience serious gas, pain and bloating after eating. When I am not having loose stool, I am constipated.

I'm frustrated and left grasping for answers. Where can I go from here? I'm scared to eat any type of seafood (which is quite limiting) for fear of dealing with the cramping and nausea.

[Dtownstew]

sorry you feeling so bad. an allergist might help to test for the food allergy at least.  Mine was able to test me for many allergies.
I hope you are not still constipated because I know how that problem is here too.
have you tried a mild laxative yet?