Hi dog&duck, as you go through puberty there are many changes to the body, and producing sweat and other secretions is one of them. Even the 'naughty bits' have sweat glands!!
Don't worry too much, Philtaz is right, but pay attention to your hygiene as Wraith mentioned and go to the doctor if they get inflamed or painful. Doctors deal with these problems all the time so don't be embarrassed.
As you mentioned the sex bit, don't be pressured by anybody to do so until you feel ready and when you do, be safe and use a condom. If you're in the UK it is illegal to have sex before 16 anyway.
Check out this link, its got good info on the subject
http://www.avert.org/teensex.htm
Take care