I don't think you are over thinking it and should test. You can get an accurate pregnancy test 2.5 weeks after unprotected sex usually. And once you've missed a period, definitely test. Now, timing wise, I'm not sure as sperm lives for up to a week and we ovulate for 24 to 48 hours, so if that matches up to when you had the unprotected sex? I'm not sure. But definitely worth a test which I'm assuming you've done by now. What was your result??