I always feel "full" even when it's time for the next meal. Is this serious?

Is it possible you're just not hungry. Just because it's time to eat, doesn't always mean it's time to eat.

Feeling full however can be a sign of serious problems including stomach and ovarian cancers, it could also be something simple like indigestion.
Have you experienced any pain or other changes recently?

If it's really bothering you should see your doctor. It's better to be safe than sorry and there are some symptoms that they'll know to look for based on the physical exam.

I agree with Gernald and would just add that gall stones/gall bladder blockage can also make you feel full. Getting older. Lack of exercise. Certain medications. Lack of good intestinal bacteria (like the yogurt commercials talk about). So many reasons.

Just a thought... have you been tested for allergies.

Coeliac Disease - which is gluten intolerance... wheat barley,rye .