First of all there are so many better places than quads. It is a very dense, vein ridden area. Shoulders, glutes and lats for the win. Second, I dont know if you changed the needle head before you switched to the left quad, but never use the same pin for two reasons. Number one is you always want to be as sterile as possible. Number two is after the needle penetrates the skin, and or the vial drawn from, it is dulled making for a more painful, bloody inject. And last, 21 guage? No wonder you are bleeding! Try a 23 or 25. Hope this helps