Found a lump in breast but had clear mammogram in January

I found a hard lump in my breast whilst in the bath last night , I’ve got an emergency appointment with my doctor on Friday 

I’ve been prodding and poking it now it hurts , it on the outside part of my breast neat my armpit 

I’m surprised I haven’t noticed ot before , it’s quite big and hard .

I had a clear mammogram in January , and had a cancerous mole removed in February . 
Would breast cancer grown this fast ???