The person in the mirror was clearly the girl from the photos. Jon looked down at his body and saw the way that his breasts pushed out the front of the t-shirt he was wearing. He reach a hand up and felt them. They were definitely real so he must have been taking hormones for a while in this reality. The next thing he had to check was a bit lower.
Jon was about to undo his pants when he realized that he wasn't wearing pants, he was wearing a denim skirt instead. He lifted the front of the skirt and saw a pair of panties covering a flat crotch. He was about to panic when he remembered that these were his special panties that contained an apparatus that helped hide the bulge of his male genitals. He was momentarily disturbed by the thought that he was beginning to remember parts of his life in this reality.
But Jon was still curious to see what other changes his body had gone through in this reality. He took off the panties and was both relieved and disgusted to see him penis. It was smaller than he was used to seeing, probably thanks to the same hormones that gave him breasts. He was then shocked to discover that his balls weren't hanging below his penis where they should be. Another memory pushed it's way past the shock: six months ago he had gone in for one of the first surgical steps toward becoming the woman he wanted to be. He had had a very difficult time convincing his parents to let him have an orchiectomy. The memory of waking up after the surgery seeing a part of the male body he hated one step closer to his female ideal made him smile.
Then he snapped out of it. He remembered wanting to have his testicles removed and being happy with the results. Results he could clearly see with his own two eyes. Jon knew he had to get out of this reality before he forgot about his own. He rushed to the door and flung it open startling the person who had been standing on the other side about to knock.