i am a 16 yr old female :$...just for your info.

in the WINTER, for the past 2 years, i get this AWFUL burning/itching feeling in my crotch/vaginal area. i have also noticed that, during the day, i do not feel anything. it only happens at night...
it burns, itches, and is just downright unpleasant!
i've tried neosporin, and it seems to work sometimes, but others, it just goes on burning!
can anybody please help me?!
what is it?
what can i do to stop it?
and why does it only happen at certain times? %-)