...insane salt cravings, exhausted.? Any help much appreciated. This is quite long so thanks in advance for reading. Also a bit embarrassed plastering this on the Internet, so please only respond if you can help.

25, female, thin, fit, non smoker/drug user, no existing medical conditions and no past history.

For the past two years however I've had a few things go wrong with my health.
2009 started with skin rashes, fevers, sweats, swollen and painful glands in neck, armpits and groin, incredibly sore throats and generally feeling rubbish. By the middle of the year, there was a giant infection (bigger than palm size) on my ankle, which became cellulitic, and was determined to be fungal.

At the end of 09, ankle healed but had increasingly worsening stomach symptoms that seemed to point to appendicitis. After 2 months finally had appendix removed, right quadrant pain resolved but stomach problems persisted.

All of 2010
-I've been increasingly tired and just feeling generally crap.
-Poor appetite, I've lost about 8 kgs (now weigh 50 and at 5'7" it's really pretty scraggly looking).
-Fatigued doing pratically nothing, sometimes after driving somewhere I have to rest a few minutes before getting out of my car.
-Sleeping a lot, sometimes will go to bed at 5pm and not stir until 7 the next morning for work - and get up still feeling tired.
-Dizzy, lightheaded, (have fainted several times after standing too long or getting up too quickly) weak (I used to be incredibly fit, running, training horses, last night I could barely lift a teapot).
-Every other month I seem to get some sort of virus that absolutely lays me out, at least a few days, the worst was a couple of weeks. During these I sleep literally around the clock, have no interest in food, low fevers, can't really get out of bed.
-Occasional headaches which also send me to bed, they're accross the top of my head and sickening.
-intermittent nausea and constipation/diarrhoea. Not extreme but enough to put me off food and add to the feeling of blah.
-dark hairs appear under chin, have to pull them out every couple of days.

Just in the past month:
-during one of these virus episodes, I suddenly got the most extreme craving for salt. I was literally eating it from the bottle.
Since then I've been eating tablespoons of vegemite daily, pouring soy sauce on everything, eating olives, Dutch licorice capers, anchovies anything salty, which is incredibly unusual for me, I've always hated salt and always found chips etc too salty - now I don't even bother with them as they aren't salty enough.
-I've also had patchy tan areas appear on my elbows, feet, armpits and upper arms - they're not terribly dark, I just look a bit dirty, or as though I've applied fake tan badly ( which I haven't)
-I've always been a very patient and relaxed person, but now seem to feel very irritable all the time - getting increasingly difficult to hide it.

The thing is - I've had a lot of blood tests which didn't show anything remarkable. I was quite sick with the leg thing - and according to my labs, nothing was wrong with me. During the appendix thing - nothing showed up. A few little things, but nothing major. All this year - nothing major.
My gp didn't know what to do with me, so sent me to an immunologist, who ran lord knows what tests - and nothing showed up. I live with two med students who seem to think it's something endocrine - I had my morning cortisol tested, and it was normal.

So does anyone know what the heck is going on?? Would an endocrinologist test something that wouldn't show up in an immunologist's tests? I can't continue like this, when I feel particularly bad I honestly don't care if I live or die. Not to be a giant drama queen, I'd much prefer to live - but I just feel so wretched that I want a solution.