It's actually more likely that you would have an more severe reaction if you tried it again, from what I understand how allergies work. As a child, your immune system was not fully developed, so maybe that is why you didn't have a reaction. But then when you had the shrimp, your body recognised it and produced a reaction. That's how it apparently works with wasp stings -- no reaction the first time, allergic reaction the second time, and the third time it's into anaphylactic shock.

If you went to an allergist, they would probably be able to test you.