Hmm? Could it be?

So I had sex with my partner 2 days ago, however I had my period for 2 days already, but it wasn't really there, maybe 1-2 drops more, but not really. I had it in there the whole day, then I slept with him, he came inside me once, so on the 3rd day my period actually came. Do I have to worry that the sperm can/could fertilize me?