Is Spotting During Pregnancy Worrisome?

i had 1 miscarriage in last march. i m pregnant again and had spotting and doctor has prescribed fertigyn 5000 and duphaston for upto 12 weeks. i m 9 weeks now. again i get to see very sligh brownish thread in my vaginal discharge. i dint see any such thing after i started taking the medicine.but again i m seeing it now. though it is very slight i m very scared cause i had same problem in previous pregnancy but no medicine was prescribed then which resulted in missed abortion in 10 weeks.my age is 25 yrs and weigh 70 kg with a height of 154 cms