Feeling sick 2 days after donating blood?

I donated blood two days ago, and I'm still feeling very tired, lightheaded, etc. I've slept 12 hours for the past two nights. I normally get 7-8, and I'm perfectly fine with that. I normally never feel sleep deprived.

This was my second time donating. The first time, I felt perfectly fine the next day. The only real difference between the two donations was that I didn't eat before this one, but I ate immediately after, which is what the nurse recommended.

I was perfectly fine during the donation. I didn't vomit or pass out or anything.

How long will it take for me to feel normal, and what can I do to speed up the process? I volunteer at a hospital, and ideally, I'd like to feel better before I go tomorrow.

I'm a 17 year old male, by the way.