TW: Death, blood ect 

Hey guys, sorry this might be a long one. 
so I've had this problem since I was young (7-8yrs old) I used to call them "visions" or a "movie" but as I have grown older I thought they would be gone but they honestly have just gotten worse over time. 

As soon as my head hits the pillow or I'm trying to sleep, my brain will think of the worst situation possible and I can't stop it. Once it ends, it either moves on to something else or starts over again but something might be different but the base is still there.
Example: my partner dying in a crash and me getting a call and going there and seeing him (like... actually seeing him dead. Full blown, his blood, his face, his eyes)  everything. I've even had some with him being decapitated or stabbed - it's pretty fkd up. 
Then it would move onto me seeing him and all my emotions. Then sorting his things out. The feeling of missing him. The funeral, so forth.
 By now I would be laying in bed, bawling my eyes out; begging for it to stop. 
They can be something that's never happened, or something that could have happened if a situation was different in real life 
I had one when I was 12/13 that i will never forget which was my mum hanging from the carport nked covered in cuts and blood. 
Or they could be about myself, dying or unaliving myself and then seeing my family's grief and pain as if I'm a ghost.
Very realistic. Very gruesome. 

I've tried listening to music, I've tried getting up and reading a book, I've tried literally everything over the last 15yrs (I'm 21F btw)... and nothing I've found stops it. I've tried overriding the thoughts with positive ones, I've tried telling it to stop, everything. If it goes away when I'm up trying those things - it comes right back. I usually cry myself to sleep most nights because of it and always have. Most nights I don't sleep until 1-4am because of it. 

I just want to know if anyone has experienced this or anything like this? What can I do?