A little worried.

My boyfriend and I don't use protection or anything, so I definitely knew pregnancy was basically right around the bend if not extremely careful using the withdrawal method, but anyways, you know where this is going. I start my period at the end, or beginning of every month, I started the second this month and ended like the 7th or 8th, well on the 10th my boyfriend and I were having sex (unprotected) I was on top, and he was a little late on "I'm gonna cum" and he came a little inside of me. I'm pretty worried that I'm going to end up pregnant. I'd like to hear from everyone. Thanks ahead of time.(: