You're a normal person living a relatively normal life. You're young and relatively comfortable will your sexuality.
One day, while you're asleep, you hear a voice call to you. "Human..."
It doesn't feel like a dream. But you can't wake up. The voice continues, "you have been selected to explore an alternate really. You will awaken there upon the morning. You will be in the body of yourself in this alternate universe, but retain your old memories. In four weeks you will wake up here again as if nothing had ever happened. We are practically interested in realities with different human relationships to gender and sex at the moment, so you will likely be sent to one of that nature. We await your dawn, brave explorer."