if you have a history of poor diet and drug abuse your problems could be simple malnutrition, not to mention metabolism problems from inactivity. if i were you i would not be in a hurry to chalk this situation up to ms.
do you have access to a nutritionist that could do an evaluation? personally where i am nutritionists are not covered by health care. but you might have adequate insurance to get looked at.
i would advise you to get copies of all your bloodwork and never to believe that the result "normal" means healthy.
check out this familiar diagram - if your blood levels of whatever test come back outside the normal range, you're in those extreme tails. you get one step inside the orange zone and presto your bloodwork comes back 'normal' (probably low- or high- normal, that is)
whatever blood work you look at, there are going to be a lot of sick people in that 'normal range'. wouldn't you love to know which part of the curve has the healthy people? it's annoying too because you can't assume the top of the curve. that's just the level the most people have. that doesn't mean everyone with that level is perfectly healthy.
anyway i hope you can find some answers! u should not have to worry about this at age 19.