A 30 years old lady underwent Dilation and curettage (D and C). She had taken emergency contraception before but still dead fertilized ovum shows hCG positive. So D and C has done at 5 weeks of last menstrual period. Still after one month of post D and C, slight spotting continued at irregular intervals.

She started taking contraceptive pills. But had no effect. What could be the cause and treatment? Kindly suggest.