I am 39 years old. i have dark circles under my armpits, sometimes a little painful and itchy. itchy and burning scalp on sides of head and hair loss?

Time to visit doc: You are describing symptoms consistent with many illnesses from diabetes, addisons disease, cushings syndrome, seborrhea, alopecia, etc. You are to young for any of your symptoms to be taken lightly and all are pointing to metabolic imbalance. You need to get a complete physical, appropriate labs,and your Doc will be able to begin to address your symptoms and treat you.