Im about 13 years of age. And i have lots of thoughts about suicide. I need help.?

My mother died in a car accident about 1 year ago along with my older brother. I live witgvmy uncle. Because my dad is in jail for life. But my uncle beats me. Hes soo agressive. He always grabs be by the crotch and squeezes until im on the floor crying. I tried to go live with my grandmother but she hates me because i slept with her 2nd husband. Every night i hear voices talking to me. Ive brought a knife to my throat several times. I dont know what to do!!!