Hi Sophie:-) First you have to try and relax. Yes there's a possibility that you are pregnant because you were ovulating around the time you had sex according to your dates, but then again the stress you're putting yourself through can be delaying your period. My advice to you is wait til at least you are 6-7 days late then you can take a HPT. Once you are at least a full week late HPT can give you a clear positive or negative. If you take the 2nd test and that comes back negative but you still don't have your period, then you have to make an appt for a blood test. that would give you you MOST accurate answer. Again, try to relax and calm down (I know it's easier said than done) Stressing doesn't don anything but add to your situation. Good luck and please keep us updated on your status:-)
There are no doctors on this forum but other people who may be able to offer advice from their personal experiences.
REGARDLESS if your boyfriend came in you or not EVERY TIME you have unprotected sex there is a chance that you can get pregnant. I would personally wait a week to see if your period shows up & if not then I would contact my doctor to get a blood test done. Unfortunately the urine tests aren't always accurate & ALWAYS need to be done 1st thing in the morning with 1st morning urine in earl testing so it's just easier to get the blood test done. Stressing about being pregnant though can cause you to have pregnancy like symptoms & can basically cause your body to mimic a pregnancy. Try not to stress or worry about it. There are SO many reasons that your period could be late including diet, environmental, stress, pregnancy, certain medications & dehydration are just a few.
To answer your next question YES it's ok to still have sex even though you are late BUT USE PROTECTION ! that way if you aren't pregnant already it will avoid it happening while waiting for your period to show up.
Good luck & keep us updated
Melissa