I give rather frequently, but if you have that much difficulty, you should probably find something else that you can do to help others. It really shouldn't be that hard on you, and if it is, you shouldn't push yourself. I have a problem if they try to use my right arm, the vein always collapses. I let someone talk me into it every 2-3 years, and it always happens, leaving them poking me about and me about to pass out. From now on, they get the left arm or they get nothing.
"It hurts so good..."