"not being able to see the doctor"

Hi I've tried to get an appointment to see my own GP since last week and keep getting told there are no appointments left.

I have had a pain just under my right rib that also goes around the back and is worse when I take a sharp intake of breath. The pain started last week and was quite severe until two days later when is eased off quite a lot but was still sore and tender. On Saturday it went severe again and pain killers are not working for the pain. Right now it feels like someone has kicked me from the inside of my rib. Although on a scale of one to ten, the pain is now only a three. On Tuesday, Wednesday, Thursday morning and Saturday the pain was more a seven. I haven't hurt myself or pulled a muscle. I think it may be either my gall bladder or my liver that is causing the pain and believe I need a scan.

If I cannot get an appointment at my own GP's again tomorrow would it be worth visiting the walk in centre? Can they refer me for a scan? Or do you have any other suggestions. My pain doesn't warrant a visit to A&E as it is no longer severe but I know it does need investigating further but I cannot get an appointment with my own GP.

Thank you.