I'm not sure if I have ptsd..

I relate to a lot of the symptoms, but what happened to me wasn't "life threatening" it was more of a childhood trauma that has a lot to do with growing up in a chaotic home. My brothers tried to kill himself twice, (TRIGGER WARNING: SUICIDE) and that vision of him holding the knife to his throat or choking himself with a belt WILL NEVER GET OUT OF MY HEAD. hence the reason I'm typing this at two am. It's really bad today and I have gotten zero sleep since midnight of last night. I just can't shake those images out of my head EVER. I can't shake off the vision of him being put into handcuffs, or my mother sobbing inconsolably. I CANT GET IT OUT. It's been three years since those things happened, and i still feel so alone and on edge that it could happen again at any moment through the day (especially since I still live with him). The images and thoughts never leave and I've resorted to unhealthy ways to try and cope. It's literal hell.

I guess the reason I'm not sure if I have it is because it wasn't a life threatening situation. I also feel like my situation isn't valid because people on here have been through worse and... I just don't know what's going on with me and I'm depressed, can't eat and I feel so alone.

I don't know what's wrong with me, can someone please help me.