Hi Cazzer,
So sorry you find yourself in this predicament. I understand how frantic you are feeling. We on this forum have all been there.
My very first piece of advice - and this is so important - please do not start surfing the net for information on this, because you have no idea what "this" is yet, and you will terrify yourself, maybe needlessly. Most lumps are quite innocent. You must not try to self-diagnose your lump. Use the Macmillan website or this one, but none other at this stage.
My second piece of advice is ring the GP again and insist on an early appointment. Be assertive and don't take no for an answer.
Thirdly, when you see your GP please don't let him fob you off. He should refer you to the breast clinic. Many GP's seem reluctant to do this straight away because it costs the Practice money. GP's are not breast cancer specialists. You need to see the specialists. Once you get your referal and see the specialists, things will move very quickly if they suspect you have cancer. And it is a BIG IF.
Meanwhile, try not to dwell on things (I know how difficult that is). Treat yourself, meet up with friends, eat chocolate, buy new clothes, get lots of fresh air.
The very best of luck to you. xxx