I have recently given blood, and it went great, but two hours later I began to have stomach pains and a headache. The next day I got a weird feeling of pain around the left side of my body from the bottom of the rib cage, up to my left shoulder, and it raps around to my back. Now I have a weak cough that won t go away and have moments when I get light headed for about 2-3 seconds. I don t know whether this is anything to worry about or if it has anything to do with giving blood.