I have been epilating for several months & no improvement?

Ive been epilating for several months now more than 6 months and i do it ever 3 days atleast.I have not seen any improvement at all! i got this so i wouldnt have to shave and have dark under arms,I put baby powder on so its easier and ive done all the steps i could to make it work but my underarms are still dark even tough i exfoliate and i epilate after i get out of the shower,it seems like im putting myself in pain every 3 days for nothing,Please any help or tips on how i could epilate better or what the cause of this could be?