Sex for the first time

Okay so I just had sex for the first time tonight and it was great. He wore a condom but I’m not on birth control. I’m still kinda worried one of his lil guys slipped ya know? So does a condom only really help and work? I felt something a little bit. Kinda like an explosion. Weird I know haha. I guess that was just a orgasm. But could someone calm my nerves and tell me I’m not pregnant and that I’m okay haha