gave blood & adrenals crashed!!

I was thinking I was stronger than I was & gave blood last week. Since then I've had TERRIBLE headaches & anxiety. Anyone else experience this? Any ideas as to what could be happening? I've been sipping on a little Sea Salt water during the day to get me through, but don't want to do this indefinitely as it can upset my stomach.

Any help/insight would be GREATLY appreciated!!

Thanks!