I have numbness and tingling in my left thigh and it feels like a rubber band is around my left groin which is worse during menstration. caused by?

I would guess this is coming from your back.: The nerve supply for these areas comes out of the low back. You can be worse during your menstrual cycle because of the extra fluid and pelvic congestion will add pressure to the nerves. Sometimes the tingling on the thigh is specific to a nerve called the lateral femoral cutaneous nerve. It is fairly common with tight clothes or people employed that lean against the counter or have a heavy toolbelt. If it's really bothering you a lot you should go see your doctor and get checked out for the possibility of a lumbar disc.

SLFCN syndro: Probably superficial lateral femoral cutaneous nerve syndrome. Recommend avoiding prolonged standing, squatting, tight clothing and weight gain. If no improvement see your doctor.