Hi, I don't think this medicine is going to help in preventing preterm labour. It is commonly prescribed for hormone replacement therapy
& is not indicated in your case. The most important thing for you is to find out the cause of your bleeding. Please go for an ultrasound
scan if you have not done already, to rule out any low lying placenta. If it is not not low lying you need an assessment of your fetal condition and assessment of cervical length. Both can be done by ultrasound scan.This if comes out normal reduces your likely hood of going into preterm labour. A CTG should also be performed to confirm fetal well being & to see how much you are contracting. If you are really in preterm labour you need a medicine that increases maturity of baby's lung. If pain is due to some other cause treatment is different. Please check your urine too, for infection. Don't forget to take rest and avoid all kind of exertion. Please take a second opinion
from a gynaecologist before starting this medicine & for your pregnancy
care. Best of luck.