Severe Darkening in the axilla. Left.

I'm 21. I am a fair to dusky skin toned girl and have had very dark underarms for 8 years. During early teenage I was very active and used to sweat a lot. I drank very less water (500ml or less) which caused my sweat to be very acidic and had a strong odour(did not use Deo or anything). It used to stain my clothes yellow. Also because i was tired, i did not have a bath immediately(directly next morning) and thus poor hygiene lead to a sudden darkening of my underarms at the age of 12-13. Doctors suggested Candid dusting powder which did not help. I tried home remedies like coconut oil and lemon and baking soda too. Another doctor recently said darkening was normal in the axilla without even looking or hearing my condition. After maintaining good hygiene and diet for 5-6 years and scrubbing regularly the darkening has not gone. Please let me know if there is any cure(medication and creams/ointments) for this or laser or some surgery is the only option left. Thanking you in advance.