Hi willy! I'm not sure if this is what is going with you, but my doctor recently mentioned a kind of nerve-pinching that causes weird sensations in the thighs (numbness, cold, heat, anything!) - he said the fancy medical-speak name which I can't remember, but I think he may have also called it carpenter's something-or-other...
Okay, enough of that: it's called "meralgia paresthetica" (I love google!). I don't know if this will apply to you, but you might want to look it up and see if your burning sensations match the areas effected by this nerve. My doctor said it's fairly common, and that it happens to him sometimes - and that it doesn't have to come from being a carpenter; it can also happen from tight pants and carrying a wallet in your front pocket, or any number of causes.
I'm worrying about MS too and I know the feeling - it can just completely take over sometimes, right? Ugh, yes, a definitive answer would be lovely. Because until you've got one, you're irresponsible for NOT worrying, right? That's how I see it, anyway. I wish you luck! :) And I'm sorry about the nerve damage.
You don't sound like a hypochondriac at all. My mother and sister have MS and I too have symptoms but have been diagnosed with only possible MS and then the neuro decided that I didn't have it. Such a merry-go-round yes?
It's frustrating when these symptoms come up and there don't seem to be any answers. And it can most definitely make us feel nutty from time to time. This is a really good place to vent them all.
I hope you won't give up looking for answers. Many of us have been told we don't have MS and eventually it does show up in the way that they want to see it.
Take care, Charley