Yes, the hives and GI distress sound EXACTLY how my DH's soy allergy works.
Sometimes he doesn't get hives anymore-- just the GI distress, sometimes really severe.
How were you tested, exactly, and what to?
Because there are some things which are much more common as adult-onset allergies than others-- and if you were blood tested, there's a reasonable chance that it was a false negative. If you were skin tested, did your allergist do a histamine control? Did it cause a welt?