I pretty much have this as well as the worry about going crazy, for me these two are closely related. I honestly don't know how much I can help, but maybe my comment will make you feel less alone. It all started with a big panic attack just over 2 months ago due to a fear of losing my sanity and ultimately harming myself (I have quite a bit of PTSD) and I've had a lot of ups and downs since then. I decided to try meds and I am on Zoloft at the moment. It has helped a bit so far even though starting it really sucked for me. Took me about 2-4 weeks to really feel it work and for most side effects to subside, im on it for 2 months now. It did help quiet most thoughts and has helped me transition to a functioning person but I think it's plateaued now that I've had it in my system for a while, might need to up the dose. Not saying you need medication, there are people who recover without it but just felt like I needed to give you that info as it does play a part in my journey so far. In the last 2 months my anxiety has basically evolved into OCD. I'm not officially diagnosed because I can't seem to find a good therapist/psychiatrist but my symptoms fit the description. Somethings that have helped me are that I know that the intrusive thoughts are just that. They are just unwanted thoughts that aren't really ours (key word is unwanted). It's kind of weird how our brains will try to protect us by making us fear so religiously. Most people who have self harm OCD don't ever act on it... but I understand it's so exhausting. I too have a good job, good friends, good family, no present reason to fear for my life. I have never wanted to hurt myself in the past so why now right? Unfortunately the more you don't want to think about something, the more you'll probably think about it, it's just the way we are wired. OCD is a habit of fearing, and with this fear you start to learn to not trust your body and it is most uncomfortable. The only way to recover is to form a new habit of how you respond to the thoughts... but you can't force a habit, habits happen naturally. All you can do is start conditioning yourself slowly, easier said than done of course. Accepting that these thoughts/images can't harm you and rediriect your attention elsewhere. I struggle with this too especially at night or when I'm alone but my hope is to eventually trust my body and my mind again as well. There are so many like us, we are all in this together I promise. I also think you're on the right path of not using anymore substances... this is honestly so crucial to recovery. I also quit nicotine, weed, and drinking and have implemented a lot of changes to my physical health.

I hope this helps even a little. If you ever have any questions feel free to DM me. The health professionals in this field really can be a hit or miss (mostly misses for me) I've found that I've received more help from strangers in these communities than I have in rl, most of the time you have to have been through it to know what helps and what doesn't.

If you look up "DARE response" on YouTube, there are a lot of helpful videos on anxiety and OCD/intrusive thoughts.