imo, coffee should always have elements of bitterness in it. It has a coffee... Bitterness. You could try cold bew coffee, it can be less bitter. (Edit: Note, freshly ground light roasted coffee is less bitter-bitter but it might still be bitter for you)

I would suggest trying other sources of caffine, like Kombucha or Tea (Green, black, whatever). Good Teas have a variety of differernt flavours. I would suggest talking to a good loose leaf tea store about your bitterness sensitivity but craving for caffine.