What's the likelihood of me being pregnant?

So on May 20 I had sex and it started out unprotected but after a couple minutes we stopped and he put a condom on. About 10 days later I got my period but it was like 7 days early. It was about 3-4 days long and pretty everything seemed pretty normal. Now, it's been about a month later and I haven't gotten another one and my cycle is usually a little less than a month long. I'm pretty sure I'm not pregnant but I'm just wondering what the chances are or how likely it is that this could happen? By the way, I'm 19 and not in a relationship so I don't want to be pregnant right now!