The tiles you have are self spacing. There are lugs on the sides or the sides are beveled outward. If you wish to get a bit of size relief sand the edge. Being a white body tile you could probably just rub it on a sidewalk. Use unsanded grout & caulk the corner.

Is that drywall mud on the wall?

Yes, I had to patch a few cracks. Is that bad?

The first row towards the wall, that you have up there, should be sanded off on the wall edge, so that it is directly in line with the tiles up above. Once you do that and get that row right, the rest of your tiles should fit in properly the way they once were. None of the tiles will look good, if that first row over to the right, is all wrong.You also need waterproofing on the drywall mud, that I see on top of the blue membrane. That drywall mud that is there, also needs to be sanded, so its flat, so your tiles will all lay flat.

Thanks Cat, do you have any suggestions for waterproofing?

You can buy waterproofing at the big box stores.

Never drywall mud that should be thinset.