First of all, I am really, really sorry this is happening. Being bullied absolutely stinks. I don't care whether there is a grain of truth to what they are saying - you couldn't be a criminal (because you would have been arrested) and you couldn't be pregnant (because you would have mentioned that, I imagine). No longer a virgin? So what? Trans? So what? You don't floss?
In any event, because they are making your life a living hell, I suggest you start talking to a teacher about all of this. Beyond this guy, you are going to be at that school for another three years and you don't need this bullshit in your life.
As for him, I am sorry. He just sounds immature. If he is siding with the cruel kids, then he doesn't deserve another minute of you thinking about him.