What Causes Vaginal Spotting After Taking Meprate?

hello doctor, i am 44 years old and had a baby girl 4 yrs old after an ivf treatment. last one i am having heavy periods and my doctor prescribed me meprate from 16th to 26th day of my periods. i took this medicine last year for 6 cycles and stopped. i had my withdrawal periods at correct time. after stop taking meprate i got my periods for 4 mother at regular intervals and was normal, again after 4 months my periods became heavy and my doctor took scan again and precsribed meprate for me. for first 3 cycles the bleeding was o.k and this month after taking meprate tablets from 16th to 26th day i started to get spotting from 3rd day onwards and it is still going on even after 14 days. some days it is a slight spotting and some days it is slight bleeding. is it o.k or shd i go in for scan again? can u please advise. thanking you in advance for yr advise.