Hey, i highly recomend trying to have an extra snack a day, plus your three main meals. just throw together a peanutbutter and jelly sandiwch together,or peanutbutter and nutella. they're all delicious. honey nut cheerios, or nachos, just take some tortilla chips, shred some cheese untop of them and throw them in the mircowave until cheese is melted.
i never let my self be hungry, and it works well for me.
of course you should really talk to your doctors for advice and tips. good luck!