It is completely normal to get hot and sweaty when you are nervous. If you want to decrease the amount that you sweat, try working on relaxation techniques to reduce your stress levels. If you feel more comfortable and confident about a test you are going to take, then you won't be as nervous and sweaty.
oh my god I think I found what I have: Hyperthyroidism. just posting in case someone else has similar problems.
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001396/