[BonitaDDs]

No problem I would think Xl cups would fit even though they are 5.5 in because your breasts seem wide but not very very big so you should be able to cup all your breast into them and still have a good room to fill them.
I have wide breasts too and the sizes they recommend by cup seem to be designed for narrower breasts so yes I don't think a medium or large would be big enough for you in my opinion.