should i be worried??

So yesterday my boyfriend and i had unprotected sex and it was going good but we were both so distracted that we didn't realize that he would cum so soon. Yes he pulled out but it wasn't completely fast enough and as he was pulling out we think a little bit got inside me (not a lot and not all the way in) and the rest went on my leg. I'm on the pill and i've been taking it for a month and i already had my period, but i still got scared because that's never happened before. I'm just wondering if i should be worried or not.