Why do i get full so quick????

so lately ive been eating only one small meal per day, today i got some broccoli soup, took like 3 to 5 bites and it felt like i ate two big hamburgers!! i had to throw up a little in order to make my stomach better. i wasn't like this before, lately i have been drinking a lot of pain pills sorta addicted to them now i can take 5 to 10 at a time like aspirin, pills like that, but im not sure if that's the case,, my appetite kinda went away a little, not fully because i sometimes do have cravings,, IS THIS NORMAL?????