One of the sucky things about high school is that you don’t get a lot of leeway stress-management-wise. If you can swing it, definitely take some time off by yourself. And eat!
My own father’s a doctor, and if yours is anything like him, he’s got the goofy idea that his children will be made healthy by his mere presence. We went to doctor’s offices much less than most kids, and when we were sick, he’d assume we were malingering and threaten us with syringes and suppositories. Strangely, I developed a phobia of needles and all things medical.
All the same, if you’re as sick as you sound, I’d think a doctor is a real good idea.
And eat! Are you vegetarian? I know that for myself, when I’ve tried going vegan, I’ve suffered dizziness and momentary blackouts when I stood up. I used to forget to eat, and the same thing would happen to me.
I hope you feel better soon!
Daniel