Feel full after a small meal

Is this a normal thing for you or has it just started? Do you feel sick afterwards and get any stomach pain? I don't eat very much because I have a small stomach anyway, but a few months ago I started barely being able to eat anything before feeling sick and being in pain, I got diagnosed with gastritis in the end.

In general I can't eat a lot of food. I recently started to notice whenever I eat food(cereal and pancakes) I don't feel good at all.

Ok well it really depends on the circumstances. I.e. your weight is fairly low already so you should be concerned if you're losing weight, you should also be worried if this is a new thing and it's lasting (i.e. more than a week) and if it's stopping you eating a reasonable (read: 2000+) number of calories. If you don't know how many calories you're eating it might be worth monitoring it for a few days to check.If those things are true then you have a few options. Firstly you can try and force your body to adapt to eating more by doing it and ignoring the nausea. Secondly you can try and eat high calorie foods/drinks so you have to consume less volume/mass of food. Thirdly you can see a doctor and check you don't have any sort of health issue causing the lack of appetite. A little exercise might also boost your appetite but if you're losing weight then be careful about burning off more calories than you're able to eat back.
Also - you've posted several threads about diets and so on recently - are you having issues with your weight? I don't know why you would be considering a diet when you're already underweight.

The struggles