You keep thinking: I did send those pictures myself after all? That voice in your head just will not leave. The person who put your pictures online or is threatening to put them online is telling you that it is your own fault. You can already envision your parents asking you why you sent those pictures and your classmates calling you a slut. It is understandable that you have these thoughts and feelings, but it is never your fault! If something like this would happen to you, would you talk about it?