Plan b??

So I've been on the pill for a little over a year now and I usually take it on time everytime I RARELY skip a day. A few days ago, I took it a couple of hours late but the next day I got right on schedule. Yesterday (july 31st) I had unprotected sex with my s/o. He pulled out but he didnt cum a lot. I dont think he came inside of me. Am I worrying for nothing?? Should I go and get plan b??

Edit: I figure it may be helpful if I tell you my period usually starts in a week.