can't add full size images to body of post

when I add an image (i.e. 600×600) to the body it will shrink it to 250×250. I’ve looked at Settings>Media and the medium size is 250×250 but even when I change the numbers it still shows images in the body at 250×250 even when the image is larger than that.

This just happened today. I haven’t changed anything and the past postings where fine.