Hello,
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Relax, if you have conceived three times that indicates you can conceive and it is not indicative of infertility.Miscarriage can be due to various reasons as chromosomal defect,hormone deficiency,infections,abnormality in the uterus,smoking during early pregnancy etc.
You need to undergo a detailed pelvic examination and investigations as USG scan,Hormonal Analysis to rule out the exact cause.Kindly avoid smoking,alcohol and have healthy balanced diet.Consider visiting an OB/Gyn for complete evaluation.
Take care!