Since you used the word "major" to describe your pain, my advice would be to stop trying different things and see a doctor. Beyond that, others have hinted at it, but I'm not sure it's been said clearly. If you try to hold the string using your fingertips only, it puts a lot of stress on the hand and fingers. The "deep hook" technique is where you place the string in or slightly behind the first finger joint. It puts much less stress on the hand and fingers and make it easier to keep a relaxed hand during the draw and release. If this is all new to you, 50 arrows a day may be too much. Try cutting that in half and focus on form instead of where the arrow is hitting - quality over quantity is very important, especially early in the game.