I have idiopatic SFSN for 3 years - all over my body. Lately I start to have differant pains in my legs. How can I know if it from ortopedic reasons or another stage in my neuropathy?

Only your neurolo0gist can tell.
Ask/see your neuro.

can tell and be sure?
Telephone calls and office visits/co-pays are cheap if you can do them. But THAT phone call is the key to starting things rolling in terms of what can and should be done testing wise. Yeah, tests can be expensive, but it's penny-wise in the long run in my book.
Had I not persued getting more testing [and I'm grateful that my insurance allowed me to do so] I would be in really bad shape about now.
Phone calls ARE cheap - getting a call back tho, mite require some persistance?
Sounds like you are in one of those 'scary places' rite now. I believe many/most of us here have been there in one way or another at times. Keep your cool as best as you can and try to articulate all the 'differences' as clearly as possible.
Hard part about all this is that we don't speak 'doctor speak', nor do they speak like us the afflicted? If we could all get a common vocabulary it'd be wonderful, but not likely.
Good luck and start dialing! 's - j