Why do I sweat so much now?

Lately I have started to sweat more. Well not so much sweat as...I just smell like sweat. I don't feel wetness or have sweat stains but about mid-day I start to smell like I have been sweating a lot. I am thin and 19 and I sit in an office all day. It is always freezing in there and most of the time I am chilly. I never feel hot or really do a lot of manuel labor. I just don't understand why all of the sudden I have this oder. I use a deoderant and spray perfume....which only mask the smell. I am also allergic to most anti-persperants. I am one of those people who will not go without showering and won't wear even the same jeans twice without washing them. If anyone who is a doctor or who has the same problem could help me that would be great. Can anyone tell me what this oder may be caused by and what I can do to help it?