See, my notion about Ganger!Amy is that she's wearing all them plaid shirts because if she really was physically pregnant, she'd just choose to doss around in Rory's shirts for the first six months, and so, without realising why, Ganger!Amy decides to start wearing Rory's shirts as well.
This is my theory and I'm sticking to it because I find it terribly romantic and also I believe it to be true (yah, based on the trufax of loads of pictures I found of Rory in, like, plaid shirts) and possibly even something that was done on purpose, like.
I have turned into a total Amy/Rory shipper, dudes. They are so freaking adorkable.