Allergy tests I have taken, for food, pollen, trees, grass, weeds, is negative. So that mens I have no allergies? Will my tongue ever swell? I'm scared

It's possible. Allergy tests only tell that you are not allergic to what was tested for. Through life you will be exposed to many things that could cause an allergic reaction. Since you have not reacted to the usual culprits it is unlikely that you will have a reaction but not impossible. Your anxiety disorder seems to be more of a problem than allergies.
Allery. The diagnosis of allergy caused by allergic antibodies (ige) requires the presence of allergic antibody; typically detected by skin testing or blod testing (rast/ immunocap). No test is 100% sensitive; this means that some persons who have ige to a food or other allergen might be missed. Other types of allergy exist and a good example is celiac disease; a sensitivity to wheat caused by blood cells.