I am going to assume you are taking pics with a phone because this ais a common phone issue. When it comes to Phones, a lot of sites have trouble registering what direction it is supposed to go in and automatically puts that image as "Facing Phone Upright". So even if you take a sideways phone pic, "upright" on a phone is up and down length.

Things that I've fixed it with. 1.Email image to myself to my computer, fix rotation, upload from computer. 2. Crop photo on your phone to re-save the image. The first one is a sure-fix I use all the time.