Possible anaphylaxis

I am 22 years old and am allergic to peanuts, tree nuts and shellfish. I was in my college class today & had an allergic reaction to something. I was sitting in class & had my and on my face & I immediately broke out in hives all over my face. When I got to my next class ( which is right down the hall), my chest felt very tight, almost like I was having an asthma attack. I started having trouble breathing and left class to call my mom to pick me up. I took some liquid Benadryl and am fine now. I believe I had an reaction due to cross contact of my desk from the person sitting there before me. They must have eaten something that had nuts in it because everyone around me wasn't eating anything in my class. I have never had an anaphylactic reaction and was wondering since I had trouble breathing, did I have an anaphylactic reaction? I'm going to ask my dad since he is a firefighter & EMT but since other people in the PA & TRA community might help me out? Thanks, and I did have my auto injector but was unsure if I should have used it & take the Benadryl & gone to the ER. Next time it happens, I will have my professor call 911 . Also, I plan on keeping wipes with me to wipe down everything I touch & come into contact with.