Check yourself medically; you might have hEDS, or some other hormonal problem. It’s much more prevalent than people think. Check T3 thyroid for sub clinical, check your Testosterone (female and males). Check for post exertion fatigue by exercising to exhaustion and trying to repeat in a few days. You could do a FMa test. The official diagnosis for hEDS is crap, so go through the comobidities and see if there are other weird things about yourself that it could explain. I spent years thinking I was lazy before finally figuring it out.