Pregnant for one month. had one early miscarriage before. afraid a lot. took rest and medicine. how long i have any further risk of miscarriage?

A couple of months: You are correct that the risk of miscarriage is much greater early in pregnancy. Remember that by the time you miss your period, you are already at week 4 of the 40 week pregnancy. At that time the estimate of miscarriage is about 25 to 30%. But a mere 4 weeks later, at week 8, the estimates are that miscarriage is down to 2-3% likelihood. Then is stays low. Good luck!