Period stopped and then started the next day?!

HAS THIS EVER HAPPENED TO ANYONE? Should I be concerned?

I've been taking Seasonale at the same time everyday since January. The only times I've had breakthrough bleeding is when I forgot my pill...this has only happened 2 times. The bleeding was never heavy like a normal period either. I've had occasional cramping on the pill too. Nothing too bad and not too often.

Well the other day for no reason I started my period. I'm not on the placebo pills either. I just started really heavy bleeding for 2 days with horrible cramps. Yesterday morning I had a little bleeding, but by the end of the day there was absolutely nothing, so I figured I was done. This morning however it started all over again. I had really heavy bleeding and bad cramping. Is this normal and how long can this last? It's really annoying thinking my period is over and waking up with a surprise.

My doctor did mention once that the longer I decide to skip my period, the better chance I have of breakthrough bleeding. What I mean is, my birth control is designed to give me one period every 3 months BUT I've been skipping the placebo pills and haven't had a period in about 5 months. Could that be the reason why?

*UPDATE*

I've also been passing these unusual blood clots, which from what I've read is why I have bad cramps. I've never really had clotting in the 12 years I've had my period. Nothing like this. They're large and they've been happening a lot lately.