Hi I would really appreciate some help with this if anyone can shed any light.

I had unprotected sex on 8th November- stupid I know. I can't believe I was so reckless and I deeply regret it. Approximately 4 and a half days later I came on what I thought was my period (I wasn't due for another 8 days- periods are usually always spot on give or take a day). I bled for two days and the third day was just a brownish colour, very light (sorry to be so graphic). As periods go this was extremely quick- mine normally last for a full 5 days.

Anyway I assumed that I had just had an early, light period but then about a week later (when I would normally be due on) I started to have really bad cramps- as though I was about to have my period. I have had these cramps (sometimes really strong) for over a week now but no period has come. I'm totally confused by this and am not sure what to do about it. Its now been nearly three weeks since the unprotected sex. Over the past week my breasts have been a little sensitive but not too painful and I'm feeling quite tired. What are the chances that I may be pregnant?

Would really appreciate some help with this.