Continuous spotting. Kindly advise.

Hi...I am currently 18 weeks 4days pregnant. I have subserosal fibroid measuring 6.4*6.2cm arising from posterior wall of uterus. I have been taking duphaston 10mg twice daily and Inj proluton 500mg weekly since 6th week of pregnancy (had continous lower abdominal pain with cramps and I am in bed rest since 6th week itself). Had relief in pain after taking these medications. However, I am having continuous spotting since 2nd of Feb. It has been more than 20 days and I am still having it daily. I consulted my gynae twice, but everything was normal In level 2 ultrasound with internal OS closed. The doctor has said that the bleeding can be due to fibroid and has asked me to stop taking Proluton injection and continue only with duphaston. I am still having vaginal cramps.  Is it normal to have this continuous spotting and shall I not continue with proluton injection. Kindly advise.