Will eating meat help me gain weight??!!!???!?

I am a 18 year old vegetarian(not for ethical or moral reasons but for health reasons) and since becoming one, my weight has plummeted, I am now 5''6.5 and 120lbs from being 135lbs which I was happy with. I want to gain my 15lbs back and have my sexy curvy body back instead of this stick with no boobs! and I have tried everything to gain weight but nothing's worked! will eating meat help me gain more weight, food like bacon, McDonald's big Macs, quarter pounders, KFC ect.. I really want to gain 15 lbs! will eating meat again help?? I have been one for a year so when I do eat meat, will I feel sick or anything afterward???