Two words BUF-FET! Ha-ha, seriously though anxiety and especially panic for me caused me to lose a lot of wieght. At the peak of my A/P I got down to 110 lbs, and I'm 5'6''.
I'm now a healthier 125, but I have the panic under control which has a lot to do with it.!
I would eat healthy, regular meals, and then suppliment with a high calorie shake or bar, to bulk up if I were you. Ensure is pretty good, and Power Bars are a classic, and not full of sat fat like some of the others
A lot of people might say, 'Cry me a river...you need to gain weight?' but until you've actually not been able to eat/keep food down, you don't know just how miserable it is
Good luck and happy eating!
S.C.