Hi Liz4
Just read what you have been through, my advice is go back to your GP and ask him to get you into a surgeon as quickly as possible. It maybe serious or it may not be, but it needs investigating NOW.
My nipple had been tipping under and was sore and crusty, my doctor sent me for a mammo and referred me to my surgeon straight away. Nothing was picked up in the mammo nor ultrasound but my surgeon saw a distinct change between it and the last one. Next was biopsy then mastectomy. Mine apparently was hidden under the nipple and had become invasive with the potential to be aggressive. I hope it all proves to be nothing for you but you need to push for an early appointment. Good luck let us know how things go
Regards
Jill