Your welcome, sorry i don't really have any true ideas other than the types of things that your blood tests should of picked up ie vitamin deficiencies, peri menopause, menopause, a virus, an infection, pre diabetes, diabetes, hypoglycemia etc, other possible causes i'm aware of are lack of sleep, poor quality sleep like from sleep apnea, mental health, dehydration, poor fitness level, breathing issues like hyperventilating, emphysema, asthma etc but there's likely a lot of others i