It is bloody awful the situation you find yourself in at such a young age. I don't know if I can offer any practical suggestions as SA is different to the States...I am not a professional and what I say here is just suggestions to look into - I have no idea if any of it is the right thing for you to do, so please don't rely on anything I say here! I am just throwing out ideas, maybe someone else in the States can offer better suggestions - the one from Sharon about the CRABS seems like a good one, as does the Montana Vocational Programme, the LDN treatment,and Lori's suggestions about taking things slow so as not to be overwhelmed.
Where I live, if you have no assets, and no income, you would see a lawyer and probably declare bankruptacy (know it sounds extreme, but someone I know just went through it). The banks (your creditors) would have no option but to write off your loans - you have no assets to attach, and no income to re-pay the loans.
There would be a problem with your Dad's assets if he signed surety for your student loans - he would then be liable for your debts, so you don't want to go there if that is the case, otherwise he would be fine as you are an adult, so he is not responsible for you legally - did the bank that gave you the loan not require you to have some form of disability insurance in case you could not re-pay the loan?
There are some legal implications if this route is possible for you - you can't get credit again until you are 'rehabilitated', nor can you be a company director - takes 5 years here for you to become a rehabilitated insolvent. Your medical bills would also have to be written off as there is no possibility of them being re-paid. But that is here - I am sure the States has it's own legalities and that they are somwhat different to ours! It may be worthwhile investigating how it works in Montana.
I can't believe that a country like the USA hasn't got some sort of programme for you to receive your medication - is there not some sort of Government healthcare? It is important that you get what your doc feels that you should be getting, and there are a few medical treatments out there, plus symptomatic treatment, and alternative therapies.
Then lastly, if you can get medical treatment sorted out, you can then spend time informing yourself about ms, and find a way to earn an income, get an education (there are usually discounted fees/subsidies for disabled people - here any way), and get on with your life - you do still have one, you just can't see it right now. Depression does that, as does the shock of ms, and the truly difficult circumstances you are now in. But, this too shall pass.
Please don't despair, I realize it seems impossible now, but there must be help out there, whether it is gaining assistance in going back to school and one day being employed, or just getting proper medical care.