My thumb index and middle finger on my left hand keep going numb and hurt along with the inside of my left arm why is this?

Get electro myogram for left carpel tunnel syndrome, in the mean time you can use wrist splint and if your doctor will like to use diuretic if appropriate. Hope it helps.

Your description would be consistent with a pinched nerve at the wrist; i.e., carpal tunnel syndrome. See a hand specialist. An EMG/ nerve conduction study will reveal severity and provide localization.

Your symptoms are consistent with carpal tunnel syndrome a compression of the median nerve at the wrist level. Other symptoms other than the ones you list could be wasting of the thenar eminence and weakness of pinch. People often describe a loss of dexterity as well. Predisposing factors are diabetes, cervical neck arthritis, and hypothyroidisim. Seek care with a hand surgeon.