sezza, you need to see a doctor. It's very unlikely this is a skin condition that can be cured with creams.
It's gone on for 3 years and from your post, there isn't an apparent rash or bites that you can see. It's not likely a topical skin problem - it's more likely to be an internal systemic disorder, like kidney problems, red blood cell overproduction, thyroid disorder, or other systemic problems.
Best wishes.
http://www.ehow.com/how-does_5270517_causes-itching-over-body.html
does itching increase at night?..any kind of pustular lesions??get checkd for scabies...it does occur at times...n check your absolute eosinophil count and immunoglobulin E...
Do it happen continuiously or just on occassions it could be hormone related,stress can also be a big factor i suggest you go to your doctors so he can run some allergy and blood tests.