If there is no physical defect, the infertility is mostly caused by the coldness of the body.
If you check your temperature, the temperature should be lower than the normal temperature (97 degrees F or 36 degrees C).
In Oriental Medicine this is a condition of weak Kidney energy.

So what should you do?

Yes, WARM YOUR BODY.

WEAR CLOTHES WHICH DO NOT MAKE YOUR BODY COLD.
In winter, everybody wears warm clothes, but even in summer, you should keep it in mind to protect your body from the cold caused by air conditioning, wearing double clothes or socks.

DO NOT EAT FOODS WHICH MAKES YOUR BODY COLD.
Avoid fruit, eggplant, mushrooms, etc.
Drinking too much water makes your body cold.
When you drink water, drink water warmer than your body temperature.
Eat root vegetables and beans to strengthen your Kidney energy and warm your body.

TAKE LONG HALF-BODY BATHS.
Half-body bathing is most effective to raise your temperature.
Continuous half-body bathing at your temperature plus 7 degrees F makes your temperature rise.

At the end, repetitive miscarriages would be caused by the same reason.
Try to warm your body by the methods described above.