M�nchhausen's Syndrome is where someone believes him/herself to be ill or where he/she actually makes him/herself ill deliberately. They do this over a lengthy period in order to gain the attention/publicity this brings to them, putting them in the spotlight, as it were. The same disease, with the added words 'by proxy' means they do this to someone else, often their own child.
These are truly pathological conditions, whereas Medical Student Syndrome is a passing fantasy....ie I had lumbago yesterday, I've got liver cancer today and I'll have AIDS tomorrow, for example, simply because these are the diseases described in my reading matter on the days concerned.
There are many websites devoted to 'Medical Student Syndrome', most of which seem to state that it is a form of hypochondria, as offered in my opening response above.
Don't worry, J, you're not alone!