Fibroadenoma?

First of all, sorry if this is the wrong place to post. 

I am 35 with 3 young kids and found a lump a few days ago - i think its been there a few months but 1st time i felt something i put it down to muscle strain or injury as i was doing weights in the gym. Anyway forgot about it as i checked a couple of times and couldnt feel it but its there now and its quite big feeling and my husband felt it too so went to the gp yesterday and she said its nothing to worry about, is the size of a marble (it feels bigger than that to me) and that it is a fibroadenoma but she'll get a scan just to make sure but its not urgent so will take 'a few weeks' i'm in Scotland so im expecting about 6 weeks maybe more? its just an ultrasound at the local hospital though not a breast clinic appointment. Anyway, i am now worrying myself sick that it is/could be something worse and i suppose i just wondered how people cope with the worry and waiting and not knowing and also any experience of fibroadenoma or think that and its not. I really dont know what i am looking for but im just worried - my great gran died of breast cancer although that was 60 odd years ago, my mum also died of cancer in her 50s (not breast cancer) and we think my gran who died before my mum may have had the same cancer too which makes me worry more i think - i've never had anything like this before or any kind of scare and im just panicking. sorry if it is inappropriate to post here x