I'm a 16 year old female and these past three days or so I've been in a constant state where I feel so so hungry but at the same time very nauseous and even thinking about eating food makes me feel sick. Even when I do eat something, I feel full very quickly and can't finish my meal because the sick feeling in my stomack comes back. And after the meal my hunger-nausea comes back in about an hour.
I'm not sexually active so I'm not pregnant. I had my period 6 days ago and usually I do feel extremely sick and bad in my stomach during it and my period always is very heavy and I have intense period pain. But my period is over now and I've never had any lasting non-welness after my period.
This situation is very uncomfortable to me and it doesn't feel better in any sleeping-crouching-any pose, I've tried.
I don't know if this is revelant to all this but I have various other medical complaints that I've had for a long time and the doctors can't figure out such as heavy headaches, very low vitamin D level, pain in bones (When I was a child I had Osteoporosis but it was cured when I was around 10) and some other complaints.
So far I haven't actually vomited yet but this hunger-nausea is driving me insane.

Goodness, your doctor isn't doing a very good job if he or she just says you have low vitamin D and leaves it at that! You need 400 iu a day, and it's a lot more important than many people realize, as well as many people just aren't getting enough from diet and sun. And with your history of childhood osteoporosis, and the need for D to absorb calcium, this is even more urgent.

I'll guess that your symptoms are related to all this, by way of your menstrual cycle. This month your period is over, but there's a good chance that your hormones are still in the same state they are when you are menstruating. Very, very few of us are the same each month, so it's just not possible to say 'I never vary.'
If your doctor knows that your D is low, it's time to see a better one. An endocrinologist might be good. The reason is that D is actually generated in the kidneys by parathyroid hormone. If there is something wrong with your kidneys, your parathyroid, or if you have something like celiac disease, you might not be getting any D no matter how much D-rich foods you eat, or supplements you take.

In short, you need some unusual tests. I am merely speculating, of course, but with your history, you need to make doctors take this seriously.