I've had a bad bad headache for 3 days and I just woke up out of my sleep feeling hot and like I'm gonna vomit this is scary I'm very afraid I may be dying right now
I am going through this rn!! I’m so afraid to go back to sleep. My pain is so sharp 
I have anxiety and this isn’t helping it. Sadly migraines last this long and can be painful enough to wake you. I hope you feel better soon!
What did you do before the headache?
Are taking a lot of stimulants like coffee or tea?
Are you taking some meds or drinking alcohol?
Are you getting enough sleep?
1-3 days of fever is very normal.
It's just a way to release some toxins from our body.
In fact, high temp kills bacteria, viruses etc.
If you vomit, did eat something usual (dairy, gluten etc.)?
Vomiting can be a way of elimination.
Your body detects that there's something wrong, that it needs to be eliminated.
However, it can be dehydrating. So you have to take sip of water.
If you still vomit, stop it, you can replace that water loss through bathing.
Of course, water passes through skin because of its small molecule (H20)
Just like oxygen and carbon dioxide.