I'm new to sex... but I'm scared.

Okay so I recently just became sexually actively last month, and we used a condom. I had my period, all was good. We haven't had sex since, not because I'm scared of having sex it was amazing and I want to do it again! I'm just extremely paranoid about getting pregnant. We always have condoms so that's not an issue. I just  get so worried that one might break or we put it on wrong or something. Any tips to calm my nerves, or do I have a legitimate reason to freak out this much?