That's good, at least you can rule that out then.
Fibroids are like little tumours (non cancerous) that grow in your uterus. They're harmless and can easily be treated with either medication or if they really effect you then can be removed by a minor surgical procedure. Most of the time they don't have many symptoms, but sometimes they can cause heavy bleeding during or between periods.
PCOS is also known as polycystic ovary syndrome. It's actually pretty common and it's literally just the development of lots of small cysts around the ovaries. It can also mean that you don't ovulate at times, release more male hormones and have missing periods. Symptoms include weight gain, acne, heavy/irregular periods, excess hair in places. This can be easily treated as well with meds or even the Pill has been known to help it. Definitely worth speaking to your doctor about and going through to check.
Also, just because you don't have 'pregnancy symptoms' doesn't mean you couldn't be pregnant. Some women get them, some don't. I don't think you are pregnant - but just for future reference it's always good to test for pregnant if you've missed a period just to rule it out. It's always one of the first thing a doctor will ask you to do if you go to see them so it's good to be able to tell them you've already done that!
im hoping that it is just nothing. i was tested for stds & it came back negative. could you explain what fibroids, and PCOS is & what are the symptoms? i know cyst symptoms can be similar to pregnacy but i havent had pregnancy symptom neither just a missed period.
Although I doubt you are because you shouldn't have bled so heavily, I would suggest taking a pregnancy test just to rule that out since you did have unprotected sex. Other things that can make your cycle go strange is hormonal fluctuations, STD (would suggest getting tested for these), cysts, fibroids, PCOS, stress, illness. Sometimes they go out of whack for no reason at all, and our cycle is just changing so it could be nothing.