I Have Had Slight To Moderate Nausea After Eating, Esp

I have had slight to moderate nausea after eating, esp in the evenings for the past couple weeks. I have also been having constipation problems for the past several days. I have gone each day. But some days had to use a fleets enema to get it to pass. Today, I did not need that, and have actually had several BMs but all are a very pale color, almost white. I had my gall bladder removed several years ago. What could be causing this nausea and pale stools?