I Am Having Stomach Issues. I Am 62 YO F.

I am having stomach issues. I am 62 YO F. I am experiencing fullness all the time, now. I sit to eat a small meal and I get full after only a few bites. I have gas, had BM that first started out with a lot of yellow color to the stool, and in the liquid coming out with the stool. Now my stool is somewhat back to normal, but the ability to eat a full meal is now the present symptom that is occurring.