2nd baby before 19??

My bf & I only had sex 3 times without condoms but took plan B after each time. We went to a mall about an hour away & walked for over 6 hours. Around the 6th hour I got a headache & felt like throwing up. (I hadn't ate or drank anything except a couple sips of my bfs lemonade & a few popcorn pieces all day. Literally.) I got dizzy so we decided to sit down, drink & eat. After eating a few bites of chicken teriyaki I threw up. After drinking fanta I threw up minutes after. I took a pepto tab & threw up minutes after that too. I felt better & took a test when we got home but looked like it was a negative. If I'm not pregnant what could it have been?