Yup, agree with all the above - we forget that it's not just baby in there, it's organs etc too, and in any other circumstance if something new were to shift them or shove them where they didn't want to go, it's going to hurt.
The worst I've had this pg was last week, I had to pull over from driving to stand up straight, as LO decided (I think) to stand up straight herself, it was agony being in a seated position. It passed after about 20mins but jeez that was unpleasant, trying to drive stiff as a board! xx