I think something's wrong with my oscar (fish)?

I have an oscar (actually two) and the bigger one always gets really excited when you go to feed him. One time, though, he jumped up through the open part of the tank (a considerably small opening) where you feed them. He got his head stuck, and I had to push the poor thing back into the tank. He was fine afterward. He didn't learn, though, and jumped up through it again a few minutes ago. He didn't get stuck but came out farther this time, and *unlike* last time, he hasn't gone back to what he normally does. Now he's laying at the bottom of the tank. He's not dead or anything, but now he's unusually lethargic and it's freaking me out a little bit. I've had him for some time and I don't want anything bad to happen to him...does anyone know what's wrong with him? Thanks.