Pregnant??

Okay so i had sex for the first time last night, and I've been non stop worrying if I'm pregnant now. When I got up earlier I felt a bit dizzy but I'm not sure if I'm just being paranoid, I know I'm overreacting but I'm 16 I don't want to be pregnant! He wore a condom tho but I haven't went on birth control yet, my last period was the 3rd of December so I'm on my 14th day, my period only lasts around 4 days I'm so nervous I don't know what to do