Malaise

According to Merriam-Webster, malaise is a noun (mə-ˈlāz, ma-, -ˈlez) defined as: [1]

An indefinite feeling of debility or lack of health: Often indicative of or accompanying the onset of an illness (such as a general feeling of weakness, discomfort, or not feeling quite right before a virus hits).

General cancer-related fatigue is an overwhelming tiredness that is often helped by gentle, tailored physical activity or structured exercise. By contrast, true PEM involves a crash or disproportionate symptom flare-up (fatigue, cognitive fog, pain) triggered by exertion that does not easily resolve with rest.

I’m not saying I have PEM but I’m not saying I don’t. 

Sometimes it is hard to put into words how you feel. That word may just be malaise.