How to clean my neck and armpits from the dark dirt?

around my neck and armpits they are darker then the rest of my skin and i would like to know how i can make it look like my other skin colour. im embarrassed to put this on but I've tried everything like many different scrubbers and none seem to work. Does anyone know how i can get rid of this embarrassment? i cant wear cool sleeveless shirts or i can't wear my hair up as im very self conscience. PLz help me with this issue. any home remedies and can try or products i can buy at the store??