Sitting that way, alot can compress the peroneal nerve behind the knee. Some people are sensitive to this nerve compression, and if done alot develop foot drop.

Looks like you have many of the symptoms of peroneal nerve compression... frequent sitting, leg crossing etc.

http://emedicine.medscape.com/article/1141734-clinical

We cannot copy portions of Medscape here so you have to join to view that link. It is free and and easy.

Frequent tripping and paresthesias and/or pain may be present.

Since you sit in classes alot at school that could be your trigger.
If you cross your legs alot in addition, that puts further pressure on the nerve. I have read that with less fat on the body, the fat pad that normally protects this nerve is lost, so it is more prone to irritation.

Seems like it may be your problem.

If you Google peroneal nerve compression
you can find more details.
example:
http://www.nlm.nih.gov/medlineplus/e...cle/000791.htm
http://en.wikipedia.org/wiki/Common_fibular_nerve
this wiki article shows an anatomical diagram.

I would hope for you in this case your symptoms are a simple lifestyle change and not CMT. So I do hope your genetic testing is negative, for your sake.