The Giving Dilema

I know this isn't really related to AS but I feel that I need some input from other people here. I try to give blood every time I am able. I used to do it more frequent but since I started giving 'double reds' I do it less often. The the Red Cross told me that I was an ideal candidate and that I was the correct blood type. Instead of giving every 56 days the time to give again is upped to 112 days; due to the stress on the body, I think. Although I feel OK afterwards it is not entirely so. For at least a couple weeks my athletic stamina is pretty much gone. I did Bikram Yoga last Friday and nearly blacked out. I laid down on the floor the entire class and felt awful. The question that goes through my mind is "Do they really need my blood enough that it is worth giving and feeling like a zombie for a month?" I heard that it is better for trauma victims and that is why I began in the first place, but I wonder if my own stress is worth it. I felt so good exercising this summer that I neglected to give for fear of losing all my stamina. Exactly what I expected to happen did. So what do you think I should do?

I don't mind helping random people I may never meet, the exact intention of his blog, but is my own well being worth it? Let me know what you think.