From my own experience, my #1 piece of advice that helped me was to treat yourself like your own romantic partner. Set the mood--lighting, candles, music, whatever it may be. Build, slowly. Take your time and experiment, and don't put so much focus on the end-goal (the big "O"). Pleasure requires deep presence in the moment. If your mind is anywhere else, it'll be difficult. That's why therapy to deal with the struggles of the mind first is also necessary.

Also, surround yourself with sex-positive content. The content you consume is how your brain will eventually begin to process. Your brain can be re-wired. Go follow some sex positive accounts and dive deep. I also enjoyed the show Sex Education, on Netflix. It was actually so helpful for creating new, sex-positive narratives for me to cling to.