Itchyness, not sure exact cause/why

I was wondering if anyone could pinpoint and/or give advice or what exactly to stay away from or what precautions to take for this situation...

Basicaly I, for about 4 years now, been experiencing very bad itchiness all over my body at certain situations.  Its happened at very random times, but 2 of the most frequent, are 1. when im working and sweating, which is way less often than 2. when i get out of the shower.  I itch mostly  on my uper arms and upper legs... but my whole body itches none the less... im even itching right now comming out of the shower, its so bad i really hold off taking showers because i hate the feeling when i get out, please can someone help me?