My first period after a mmc and then d&c was light. My second is extremely heavy and painful with lots of clots and extremely heavy flow. Is this ok?

No. If you are having pain and heavy bleeding you need to see your doctor to find out what is going on and get treated. Don't wait until you stop bleeding. Go now. Best of luck.
Irregular Menses. Irregular menses is expected with recetn hormone changes related to pregnancy and D&C. Check pregnancy test to be careful and then do not worry. This irregularity is expected.
Probably not. There could be a number of reasons why your flow is heavier and painful. It may be hormonal or a delayed complication from the procedure. You will need to see your gynecologist for evaluation and probably further testing. For now until you see your doctor try some antiinflammatory medication like Motrin (Advil) or Naproxen (Aleve) to help with the pain. Take care.