I'm 15, and its gotten into winter now, and for some reason, my joints have started acting up... starting with the joints in my fingers feeling discomfort, sort of creaky and painful, with the discomfort extending from the joints further along from the nuckles to the end of the fingers. Then I started getting similar things in the toes as well.
The other day, I started to actuall feel discomfort in one of the hip joints (where leg connects to pelvis I think) and I've actually been able to feel the hip joint move when I walk.

I'm only 15, why am I getting joint pain? I've also noticed a slight decrease in joint mobility in those areas.
Is it just because of the cold weather? My joints have never acted up because of cold weather before this winter.
I have feet that roll in, which has screwed up everything above (one leg longer than other, spine problems, shoulder and pelvis wonky, I wear orthotics in my shoes and have a wedge in one shoe)

You sound like you have arthritis-it's actually more common in teens and early twenties than most people think-go to the doctor, it may be controllable, through medication and/or lifestyle changes.