Something that has been bothering me for a while?

Occasionally, when I'm falling sleep, or just walking out at night to take the trash out, I get some seriously HORRIFIC mental images in my head. Often about finding my loved ones murdered, or what not. When these images happen, I get TERRIFIED, and have to run back into my house for fear that these things might actually happen. I'm sixteen years old, and I do have a sort of dark history involving sexual abuse. So I was wondering if that's all connected, and how I can get these things to stop? I also get freakish nightmares, and I hate falling sleep because of it. The only thing that helps is if I have some sort of sound on when I'm going to sleep, be it the radio of the simple whir of the ceiling fan. I don't know what to do about this, and it's really freaking me out. Also - I have thoughts of suicide on occasion. Not that I'd ever actually commit it, I just wonder what people would think after I go. Would the miss me? Would things be better for everyone? Those sorts of things. I just want it all to stop, and I want to feel NORMAL.