Different periods - changed beyond recognition

OK...for the last 20 years I've been blessed with short periods. 100% clockwork in their length. Could absolutely predict when they finished each and everytime. 100% guaranteed 3 days and 3 nights (or 3 nights and 3 days)....NEVER EVER so much as a day (or night) longer. 2 lights days, one heavier day in the middle.

My periods started when I was 13, and now I'm 33...and in the last few months (4 or 5?) they have changed beyond all recognition. Now they are significantly heavier....for instance I used to be able to use Tampax Regular the whole way through, changing just twice in 24 hours for all 3 days. Now I'm having to use Tampax Super Plus, and change it every few hours...HUGE difference right there! And they can last anything from 6 to 8 days ...gone is the regular predictable 3 day routine.

I'm also noticing huge blood clots, which I never really noticed a lot before (although I guess I had the occasional one)...and terrible cramps which seem to directly correlate with the arrival of a clot.

Always had the normal cramps before....but now they're more regular, last longer and hurt more.

Anyone experience a change like this before? Any ideas?

All info greatly appreciated

Cally