I've had all liquid diarrhea for 4 days, first dark green, then yellowish and now pale yellow. no vomiting or fever, just fatigued. when should i seek?

Very soon.: The fatigue concerns me. Even though you aren't vomiting, you could still be getting dehydrated. Or, worse, you could have an electrolyte imbalance as a result of the severe diarrhea. I encourage you to continue to drink a variety of clear liquids until then, but please seek medical care as soon as possible.

Enteritis: I would try, first of all, to reduce my food intake. I would start with a clear liquid diet for 24 hours and then gradually increase by adding more nutrient fluids and then as the diarrhea gradually stops continue to increase my intake. If this does not help please see a physician

Drink gatorade: If you are unable to rotate oral foods or not feeling better, would see your pcp as you may be getting dehydrated.