What Causes Severe Abdominal Cramps And Heavy Bleeding Post D&C Procedure?

Hi I m 34 yrs old.I had d&c in November 2014 after missed m/c at 8 weeks.After that I got my periods with in 25 days.That period looked pretty normal for 6days as my bleeding days r normally 6.After that I received my period on 31st day of my cycle.This time fro 2nd to 4thday I was passing clots.,with heavy bleeding.That was not normal for me..but it was stopped as usual on 6th day.Now I m on my eight day of cycle feeling bit of pain on my left side of lower stomach .I am worried if I can get some serious problem after d&c in conceiving again as we r ttc now again.Why m I having this heavy bleeding ? Do I need a ultrasound to check what's cause pain or heavy bleeding.