Pain in side

[MurunBuchstansangursCousinRossiter]

For about the last week I’ve been getting pain in my left side. It started sort of slightly towards the front, then moved to literally the side and sometimes it moves slightly towards the back. Defo in the side area generally though. Sort of waist level.

Mostly a dull ache but sometimes gets a bit worse and feels like it’s pulsing/spasming.

What could it be? Probably I’ve slept funny or something, right?

Not appendicitis as thats the right hand side.
Could be a muscle strain
Could be gas?
Endometriosis, ovulation, pmt ?

Gastritis maybe or Acid Reflux.