Breast lump

I'm waiting to go to my breast clinic appointment on Tuesday...I shouldn't google anything, I'm terrifying myself! 
I found a lump on Sunday and saw my gp on Monday where she confirmed she could feel a hard lump (that doesn't move) it's about 4cm x 5cm. Yesterday I woke up and can feel a lump under my arm which is tender to touch and definitely wasn't there when I saw the gp 2 days before.
I have everything crossed that this isn't as bad as I'm imagining, with two small boys aged 3 and 5 my mind is racing, my hubby is very supportive and I know we can deal with anything but roll on Tuesday when hopefully I can get more info! 
Is there anything I should be asking when I go to my appointment?