What are the chances of me being pregnant?

Alright this is a really important question and I need good answers. So the other day me and my boyfriend were having sex, and well the condom broke about 15-20 minutes into it, as soon as he heard the snap he pulled out. He did not cum inside me. And it...

was like the last or 2nd to last day of my period (which lasts about 5 days). I was wondering what the chances are that I could become pregnant. Also this Sunday (tomorrow) I'm starting on birth control. Should I not take it? I mean I'm not sure weather or not I could be pregnant, and I don't to take any chances if we do decided to have sex again. Right now were taking a break from it. Aha. We've always been very very careful and this is the first time anything like this has happened. I really could use someones help right now. I'm stressing. And please don't tell me I'm too young or something stupid like that. Cause your opinion on my life doesn't matter. This isn't a site to judge people on their life, it's to give advice and advice only. Oh, and if it matters today is Saturday and this happened on Wednesday. Thanks in advance.

if he stopped when it snapped...then chances are slim that your pregnant...if pregnancy worries you...then stop having sex...easy solution