Polyhydramnios, does present differently to GD (although I was not suggesting that excess fluid is a result of GD either) However the OP is 22wks along - nearly all cases of Phd start after the 30wk mark. Most wm with Phd notice a sudden increase in the size of their 'bump' as the increase in fluid is marked, often trebled.
Polyhyrdamnios started for me at 24 weeks and same with a SIL of a fellow BB'er (she may have been even earlier), my bump grew bigger but it didn't look that big TBH, and it was the fundal height that suddenly showed me a lot bigger, and in this pregnancy I have compared my photos and at 24 I looked a lot bigger in the bump then I was at the same time as I was with DD yet no Polyhrdramnios....

The scan does not need to be done after 30 weeks either... it really needs to be checked earlier and further testing to ensure that it isn't the result of an infection or GD. I came back clear on both accounts with DD, so we never found the cause.

And I can say there were a lot of waters when they broke at 33 weeks