I am so sorry you were raped as a child and bullied.
I was sexually abused as a child. Unfortunately, every single thing you've described is something even I experienced....as do many people who are sexually violated at a young age. It would start as viewing/reading something taboo....the act...the finger numbness....feeling miserable, guilty afterwards....telling myself I wouldn't do it....and yet do it, the very next day. I was also into porn stories which got wayyyy degrading over the years. I still cannot imagine something romantic.
Please do checkout wikipedia page on child sex abuse or search adult survivors of child sex abuse, and you'd see that compulsive masturbation is one thing they experience as adults.
I have slowly got away from the habit (just compulsive part) and my stories have got a little less taboo over the years, but I still do slip back, but happens once in a blue moon.
I can understand that you currently cannot afford therapy. But please understand that therapy is not luxury, it's necessity. Are you currently working? If not, even the tiniest job can help pay for therapy. If yes, then do save - maybe in a piggybank (i know it sounds childish). See if you can afford online therapy. Online therapy has its benefits - like you can be more open, you can look after your convenience and even read emails at night, your conversation history is available.
My therapist once suggested writing about negative incidents are burning it up. This was surprisingly useful. So do write and burn it. Also, writing, in general is very helpful, you start developing a little acceptance.
Until you enter therapy, you can read self-help books. The Body keeps score is a book written for ptsd and it's very highly rated, so you can start up on that.
But ultimately, you should look going into therapy.
And I want to add, there is nothing dirty about masturbation. It's a very healthy habit....and the purest form of I

ME. It's the stories that make it feel horrible. When you are violated, brain seeks to relive the trauma again and again to get some control over the situation. Try to avoid taboo....let your mind have a free run. If you fall back into habit - it's because your mind is still looking to gain control over it, don't fret too much over it. Just keep trying and give yourself some time. Trust me, you'd get better with healing, as did I.
All my love.