Kiwana

You were a human man left on Pandora after the other humans were pushed off. In order to make survival easier, all remaining humans on Pandora had to have their minds permanently transferred to a na'vi avatar body. You were the last one, and the only avatar left was a female body. In order to survive, you had to be placed in her body, but you were not told this would happen until you woke up in a woman's body