Lump under lower left ribcage, help?

[Taradorff]

I've been having terrible pain and pressure under the left side of my rib cage, also sometimes a soft squishy lump pops out where the pain is and I can push it back up. When I'm moving especially bending that "lump" I feel grinding underneath the rib. Its incredibly painful and I tried to have the gp feel it but was unable to pop it from under rib, she dismissed my concerns but its im extremely worried about what it could be :(