Ok, first - here's how ovulation works: (Not on birth control) If you have a 28 dya cycle, meaning you get your period every 28 days then you basically ovulate on the 14th day of your cycle. It depends on where you were in your cycle on 5/3 when you had sex. See if you can remember when you started your last period - literally the first day of bleeding. Using that as day 1, count 14 days and that's when you should have been ovulating if you have 28 day periods. Longer cycles (more than 28 days) your ovulation day will be farther out - 15,16,17 days. There are many things that can make your period late - being sick, being stressed, diet, etc.
If your period was due the first week of May and you only had unprotected sex that week, you really should be fine. If your period is late now you can take a pregnancy test any time. If you are not pregnant, this would be a good time to start some type of birth control. Hope this helps
There is alot of things that can make u late! If you think you are preg. you will stress about it ALOT! Stress is a big cause of late menstral cycles expecially in teens or young adults!
The same has happened to me an it turned out to be my period. But soon after that people told me I may have miscarried. Good luck to you. And let me know what happens.