That's unfortunate that this person betrayed your trust. Don't hate yourself though, he shouldn't have screenshotted it.
Was your face in the pictures?
If this person shares the images, I really suggest you report it to the police.
You are under 18 and therefore a minor. Being in the possession and sharing illicit pictures of a minor is seen as owning and distributing child pornography, if not more.
Have you spoken to anyone else about this? A school councillor etc?