Do you use an iPhone? If so, give up. I gave up a long time ago and only upload landscape photos to save myself the headache.
What I do is open/rotate/save photos in a separate program in a computer before posting. That solves the problem, but this make photos not fully displayable. I wish there is a simple click button we can use to rotate photos in the website.
Microsoft Paint is an old standby, but it might be your answer here. Open the image in Paint, click save, and then upload it. I have had this problem on other websites, so I have just gotten into the habit of doing it automatically now.