I just started playing the bass clarinet and it has been going great but yesterday something happened and now I can't play any notes below a C or above a G. The moment I go below C it starts to play really high notes without me pressing the register key and I can't even get out notes above G.
This has never happened before and I can't see anything wrong with the outside of the Bass clarinet and all the keys work properly.
Do you have any advice on how to fix this?

You obviously have one or more leaky pads. As a newby you should take it to a repair technician. He could likely show you how to test for this.