Late period

My husband and I had sex New Years eve/day while very intoxicated. I don’t remember either of us finishing or what not. He swears we didn’t. However, my periods are always in time and i haven’t missed one in almost two years. That being said, I’m three says late. Also a few days after sex, I was spotting. Not enough for a pad or tampon, just when I’d wipe. Never happened. And that was gone in about three days. I know it can’t be implantation beefing that soon. The night/day we had sex was one of my higher ovulation times. I’m very confused......