Welcome to our forum. I am sorry to hear about the pains that you are having. I am not a doctor, merely another cancer warrior, so I cannot tell you what is causing these pains, but it doesn't seem right for someone of your age to be suffering like this. You have done the right thing by making an appointment with your GP, even if you have to wait for a few weeks to see someone.
If your pain gets any more severe you could always present yourself at the A & E department of your local hospital. This might get the ball rolling a little quicker for you. Before your appointment, try to write down as much detail about these episodes as possible giving dates of when they started, how long they last, etc.
I do hope that you get to the bottom of this soon. Do please keep in touch and let us now how you get on. We are always here for you.