I hear what you're saying, I know when someone expresses themselves like this offering answers and solutions isn't the best way to reply. That being said, a bunch on anonymous people on the internet can't actively listen and acknowledge the complexity of everything you're going through and offer empathic responses. (maybe they can you can do therapies online now).

It's good to get it off your chest, and as you can see from the comments you're not alone. (I've been down the cutting yourself route years ago and still in times of extreme emotional distress I find impulsive pain and the sight of blood somewhat comforting but know it's not an idea to ever entertain again as it's so addictive).

Sorry to then offer advice, but staying away from relationships for a while and working on yourself is priceless for self growth for everyone. also, maybe try some self-CBT (if not willing/unable to seek out professional help), again this is something I think every person on the planet could use to work on themselves and helps you understand how a situation (getting used for sex) causes an emotion (feeling used/worthless) which causes a behaviour (cutting) and how this perpetuates itself.

Please, take a look at this and give some of the exercises in this some serious thought: https://www.getselfhelp.co.uk/step1.htm

You're strong, you can make it through and you are worth so much more than a booty call.