How to be strong???????????

im 16 years old. :( i know, i was just a kid when i sent pictures showing off my body to a guy (not much i mean) my sister who's eighteen years old keeps blackmailing me telling about that. im in a peaceful relationship right now and she tells lies about my guy to my mom :( he doesnt have a fault at all. i cant act against her cuz she keeps hinting my mom that i've done worse stuff. she nearly did. i even cut myself. no one knows about this but her. i dont hate her, i love her so much. :( but im being emotionally harassed. i feel like a carpet. i feel like killing myself. i know what i did was wrong. i understand. i hate my life.