I found a lump when I was 31 and panicked because my nanna lost a boob to breast cancer in her 60's putting me in the high risk category. My GP sent me straight for ultrasound and mammogram and I was told it was nothing to worry about. It hung around for quite a while after that (a couple of years), but after a year of breastfeeding I think it is gone. One of the reasons I have continued with the BF is as insurance.
All the best, but if it were me I wouldn't be waiting three weeks, I just don't think that is fair at all, even if your GP doesn't think the lump is going to turn out to be anything. From finding it to getting the good news was 3 days and that was enough for me.