43 yrold w normal periods to date.had 40 days b/t cycles and light period lasting 4 days. 2days later woke up to extreme heavy bleeding and big clots?

Not normal: Most commonly it is from not ovulating. I would recommend running a pregnancy test. When a woman over 35 has very heavy cycle, she needs to be evaluated to make sure there are no precancerous changes taking place in the uterus. It would also be a good idea to check your thyroid levels, a blood count and probably for diabetes too if that hasn't been done recently.