Scared but feel stupid

Hi everyone, so sorry to bother you all I'm just wanting a bit of advice/reassurance and a bit crack really. 
 

im a 31 year old mother of 4. About 3 weeks ago my breasts started hurting a week later my period arrived so I just sort of thought it must have been caused by that time of month, my period ended a few days ago but since then my left breast feels weird, it feels achy/stingy and heavier, doesn't constantly feel heavy it's weird it kind of comes and goes. 
 

I rang my Gp for reassurance and she said I have to go and see her tomorrow morning, and said it needs checked (which I know is good) but I'm the kind of person that always thinks the worst in things and im absolutely terrified. I feel stupid but I've got allsorts running through my mind