If you get full, you don't have a problem.
On another note, I am doing Ramadan and i have lost over 5 pounds already! xD
I feel my stomach is getting much smaller.
Don't go eating unhealthy, just eat bigger portions of good food, like fruit salad for breakfast with a smoothie and a vegetable omelette for lunch or something, but don't feel you have to starve yourself.
But TBH i think you just have a really small stomach. Drastic weight loss is a problem so always make sure it isn't happening.
- It sounds a bit stupid, but i hope i helped.