Sex for the first time?

I'm 18 yrs old and i think i had sex for the first time because we stop before it could go any fared, we didn't had a condom so we stop. I was on top but after my stomach hurts like i'm hungry plus i caught a cold but not badly just for two days then like 3 days after my tonsils hurts. I don't know if it's just normal or i need to see a doctor??