Over paranoid?

My name is Billie, im 16 & about 3-4 weeks ago my boyfriend and me had sex for the first time; well it was my first time. Neither of us planned on doing it, it just kinda... Happened so we didn't have any kind of protection. We did some things to lead up to having sex and he also didn't want to risk getting me pregnant so he wasn't in me for very long, and when he was he would uh pull out and... Um.. Take care of him self for a few seconds ANYWAY he pulled out and didn't release in me but... All I can think about is "what if I'm pregnant?" I had my period about 4 days ago; it lasted for roughly 6 days. I'm pretty bloated and i can't help but fear I might be having a baby growin inside of me... Help?