How can I gain about 18lbs fast?

I keep tryna gain weight, but I KEEP LOOSING IT!!! Ugh, I'm SO frustrated! I need help... all there is to eat is pb&J nd freakin frozen dinners, nd pot pies. OMFG! How can I gain weight... eat like 10 sandwiches a day? WHAT DO I DO?! Um... any suggestions on what foods to eat, nd how much to eat? seriously... nd don't say nothing stupid like fruit nd veggies. >:/ that DOESN'T make yu gain weight!!