Man I wish I were some of you guys in the "lose weight" boat.

I'm 5'6", checked in at 126 lbs this morning on the bathroom scale and I've had Type 1 Diabetes for about 2.5 years now. This is the most I've weighed in my entire life.
I'm struggling just to maintain my weight in the 120s. And that's by eating morbidly every day. I eat on average 9-10 times between waking up and getting back in bed. Often I wake up in the middle of the night and fix myself a sandwich or a bowl of cereal. I like to think I eat healthy, though I could afford to pass up the teriyaki chicken more often. I never exercise efficiently outside of maybe rollerblading once or twice a month, and most of my calories are burned by walking around at the mall.
I checked into the ER after blacking out on the living room floor in the middle of my 16th birthday party. I had dropped 21 lbs in two days, since my one year check up had just been the same week and I weighed 118 lbs. My blood sugar was so high that the glucose meter at the ER recorded an error and I had to get tested via urine; the result was over 1000. It was the most insane day of my life, especially considering normal blood sugar levels for the average human being reside between 75 and 120 with very little fluctuation.
Would getting out to the gym a few days a week and building some muscles up result in a weight gain? Because eating almost every hour of the day damn sure ain't helping much!

-SAV