Let’s face it, if you’ve had a c-section, they rummage around in there quite a bit.
Before I had mine, the midwife was talking through what I might feel during the procedure. No pain, but a sensation she described as feeling like someone was doing the washing up in your stomach - and she was bloody right! plus I’m assuming they must cut through various muscles etc.
Doesn’t seem unreasonable that things have shifted around in there, might be a bit of scar tissue adhered to another organ, might be a floating rib as pp have said.
mine feels closer to a muscle cramp, and I usually get it when I’ve been sat slightly twisted/awkwardly, and then when I can bear to move, it seems to untwist itself. I’ve had scan etc, but unless it was happening during the actual scan (in which case I’d be screaming) I can sort of understand why nothing shows up.
guess it’s a bit like javelin arse - millions of women get it, if you go the the GP about it you usually get fobbed off - so we’ve never really mentioned it to anyone else, and only now realising how common it is!