Weird muscular pain

[Dr Jekyll]

For years I've occasionally got a pain in my right side, often when bending over like getting out of a small car or putting boots on, and it's getting worse and more common.

It used to feel like a bit of muscle was trapped between my ribs, now it's more like a cramp just below my ribcage or behind my lowest rib. Only lasts a few seconds but very painful.

Any ideas?