For the last few months i wake up every night around 3 am drenched in sweat but cold. what could be causing this?

This sounds like true night sweats, which usually are caused by fever that breaks during the night. Take your temperature a few times a day to see if it is elevated. If so, there are too many possible causes to guess -- even a common cold can do it. If you have unexplained fever and/or continuing night sweats more than a few days, see your doctor for exam and testing. Good luck.