Head Spinning:
Have you never heard of the euphemism getting spun? That's actually normal...
Cross-eyed:
Could be the result of getting a strong high...Have you ever seen someone after they shoot the shit? They look like a goddamn wind-up doll with their robotic-like movements, their jaw is opening and closing and is usually not centered, and their eyes could be going any which way...
Head Ache:
Could be the result of peripheral effects...namely vasoconstriction (constriction of blood vessels) which has been shown to cause some migraines/headaches...
Chest Pain:
Could once again be peripheral effects...chest pain (angina or cardiovascular related)/tachycardia, and heart palpitations are common with many stimulants...
Fever:
Well, I'm not sure on this, but I would assume that CNS stimulants could very easily elevate body temperatures, even if by only a small fraction of a degree...
Nausea:
Smoking too much dope (ice) can do this. It's happened to me a few times when I blew down around half a g or more in one sitting...
Trouble Swallowing:
I'm not sure what causes this, but I've had this issue when I've smoked too much in my earlier dope days...Water wasn't a big issue, but if I tried to EAT anything (especially if bread was involved) it felt like it was swelling up in my mouth and was really painful swallowing...This normally only became an issue if I had been up for 3+days not eating...the longer you go without eating, the harder it is to get shit down...
Neck/Back Pain:
I'm not sure where this is coming from, but if it's been caused in anyway from the drug usage, it would more than likely be completely indirect.
Or as atm stated you could have had a panic attack...anxiety can cause/increase pain so that makes the back/neck pain make more sense...Or you could have just had a bug of some sort...
I'm glad most of your problems are gone, but I hope your back pain subsides...
Good Luck to you man...