Suggest Treatment For Infertility

Hai...Im Rishla...25yrs(female).Im married for four yrs now...i conceived after one year after taking some multivitamins from one of the famous doctors in our country...im from Sri Lanka. Then after that saw some blood spots...in 3 months,then my pregnancy continued until 5 and half months when i had a miscarrige. Then again i conceived after 6 months...in 3 months i had cervical knots...but again it failed...again i went through a miscarriage at the same time(5 and half months). Now its almost one year and a half since it happenned....and the doctors still are trying to find the problem.They say there is a small cyst but that is not the problem.please help with afew suggestions as to what i can do next because i dont want another miscarrige.please help me...please.