I know its not what you want to hear but you should see a dr. If your form of protection was only bc it is possible that you could have gotten pregnant. I did on bc and my dd is now 16. Like you said, changes can occur and your period may get clumpy sometimes and you may experience difference in cramping but better to be safe than sorry. Just to stop your stress and worrying get a checkup. good luck
To me, everything sounds pretty normal. I know that my periods have changed over the past few years, for the better (thank goodness), but I don't see why someone else's periods couldn't have changed for the worse (more cramping, bleeding, etc) from what they're used to.
Cramping so badly that you had to leave work is very inconvenient, but not unheard of. I used to get those kinds of terrible cramps. I'd have to realize they were coming and take my Tylenol ahead of time because if I didn't I wouldn't be able to stand up straight. Also, the part about minor pains and the blood being clotted sounds normal to me - especially when you have heavy flow.
Even with that being said, you definitely need to see your doctor. While the symptoms themselves you're describing sound fairly normal for a period, it is a bit strange that this has happened to you over just 3 months. When I said that my periods changed, that was over the timeframe of a few years. So, definitely make that appointment.
Good luck!