Uncomfy kidneys when bladder is full

Smilie • Hello our first baby girl is on the way on the 22nd November 2015... Please be a sticky baby 👼 ✨BD to all
Hey ladies need to advice...
When my bladder gets full in the morning when I wake up I feel my kidneys/back hurt a little bit and it feels like someone is holding my waste line tightly I couple of minutes after I go to the toilet I feel fine. I have the doctors today so just wanted some comments to see if anyone has had this. I am 18w+1d pregnant 😔 just a bit worried