OMG, There is many of us :'''),
Thank you Koko_girl for raising this topic, it makes us feel like we belong somewhere,
I have discover my gluten/Diary intolerance about 6 months ago and since then, I've been on a gluten/diary-free diet.
my doctor said that in the path of 6 to 12 months i will be starting to notice some weight gain :''), but unfourtently non of that happened,
am 39-40 Kg and 164cm, which is extremly under weight, and i've been under weight my whole life.
the doctor said that due to my gluten intolerance my food habits was very bad since childhood, because whenever i eat food i feel bad so i avoid eating,
she said its a habit thing that should change with time,
i guess it could help to count your calories intake daily and make sure that you get more calories than ur BMR (Basal Metabolic Rate) by 500 cals at least.
also, try healthy food suplements like Opticomplete from Optinutrition, you can order it from www.Windhawk.com since its not avaliable in UAE. it has almost 1500 cals a scoop with vitamens and minerals. you just need to double check if it is Gluten free
Gud luck all :''') <3