What I would start doing is keeping a food diary in conjunction with a list of your symptoms. It may not be that certain foods are causing your problems, but even if you can't connect it to food, you will have a list of symptoms and times to take to the doctor.
Ultimately, what you may have is a food intolerance rather than an allergy, which wouldn't show up on an allergy test. If it's not an IGE mediated allergy (the kind that the allergist would test for), at least you wouldn't have to worry about an anaphylactic reaction, but intolerances can still make you miserable - just ask me when I'm foolish enough to eat ice cream without lactaid. Hopefully if it is food related, a diary will help you link things up so that you can try eliminating a few things at a time (do not start just cutting out major food groups completely without talking to a doc) to see if it helps. I have a combination of life threating allergies and intolerances - my allergists viewpoint is that while I don't have to worry as much if I was to accidentally ingest something that is just an intolerance, it doesn't make sense to eat something that makes me miserable, as long as I'm getting a balanced diet.
Another thought - have you been tested for celiac? I don't have any experience with this, but there are a few board members who do - hopefully they will chime in.
I will say that your combination of hives and stomach cramps is very much how my soy allergy presents when I've been accidentally 'soybeaned'. While I can't compare the abdominal pain to labor pains, because I don't have experience with that, they are definitely curl up in a ball on the floor and cry pains. The only worse thing that I can remember is getting my dry sockets packed after my wisdom tooth extraction - and I passed out and woke up on oxygen when they did that.