Too Full Too Quick

I don't understand it fir nuthin'!! I can't seem to get enough calories in the day. I eat 3 meals, and 3 snacks, and STILL can't get up to 1600 calories. Today I'm at 1190. I don't understand it at all!! When I eat, I get full as a tick, and can't possibly eat any more. Maybe I could add more to the snacks. There's an idea. A glass of milk or maybe 2 cups of fruit instead of one. This is truly an amazing situation for me to be in.