I honestly think that if the HPT says negative then you are not pregnant. There are many reasons why AF could be late or skipped this month. Stress is one reason. Another is excercise. Have you had either lately? Sounds like maybe the stress from your breakup may have been stressful. I would just relax and be patient and AF will show up when you least expect it. If you want more answers I would visit your OB, Only your OB will know what happened. Good luck.
There is only a 1% chance that you are pregnant if the tests have came back negative. I know being stressed may not have caused the delay in your period, but its weird, every time I've had a delayed period it was either because I was worried about being pregnant, or really hoping I was, and every time the test came back negative, it turned out that I wasn't.
You did have intercourse at a really bad time if you are hoping to not get pregnant though, as your the most fertile then. But being someone who was trying for quite awhile, I can tell you that even if your having intercourse at the exact right time, it still only happens 25% of the time. I'm betting that you will get your period soon. Then, just make sure you are more careful next time :)
dont stress too much. you're stressing now and even tho you never miss a period no matter how much stress, your body is still changing so this may be a new thing. the fact that you're stressing now probably isn't helping. I cant explain the cramps the day after having sex but i can tell you that you wont feel any changes when your pregnant until your about 2-3 weeks along. bloated tummy is most likely because your supposed to start your period. please dont worry too much. every test has come back negative. dont freak out until you know for sure.