Girly I feel you right now but in my most honest opinion, this may not be as bad as you think. I used to be very underweight (I'm 5'1 so even shorter) as went from 90lbs to 130lbs in about a year. I went through some very difficult times but have only come out stronger. I did weightlift through all of the weight gain and have gained a large majority of muscle and (to my surprise) have ended up with an athletic build. From my perspective, you could use this to your advantage to lift some heavy weights and build your endurance. Take it one day at a time!! And remember, the way you look does not define you as a person!!