Numbness/Pins&Needles

I'm a healthy 17 year old girl, about 165cm 56kg, never had a any major health problems before. In the past year, and especially in recent weeks, been experiencing excessive pins and needles and numbness in arms and legs. Sometimes it feels like my arm(s)/leg(s) have gone to sleep, totally numb and difficult to walk or move, other than that the normal tingly pins and needles feeling that I get ridiculously quickly in almost any position. The feeling fades as quickly as it comes, but surely its abnormal to get pins and needles this often? Aside from that, the muscles in my arms and legs are feeling quite weak which is unusual because generally I'm very fit and active. Anyone have any idea what could be wrong, I'm trying not to be a hypochondriac or anything but I'm scared its more serious than it sounds.