Probably a lot of people here have had, or regularly have had similar thoughts like that Chilly. I have a background where I went through all kinds of stuff like that.
If I can suggest a few things... 'Intrusive thoughts' are just what the mind does. They're not us. We're inside our minds somehow, watching those thoughts, yeah, but thoughts simply arise. And they can be as meaningless as ads on tv, regardless of how convincing or 'true' or scary they may seem at first.
And thoughts become particularly troubling when we believe them to be true in some sense. But we're just getting confused. "True" is something like the feel of the chair underneath you. The colour of the wall across the room. The person nearby and the sounds that they're making. That's the world, the stuff you can't argue with. Thoughts are just temporary, a strangely vapid mixture of images and words that appear inside us somehow, then disappear as soon as we stop paying attention to them.
And our minds are SUPPOSED to do that: give us a sort of continual stream of stuff to stare at if we wish to, or to ignore if we don't. To believe in, if we want to get confused, or even to be entertained by if we decide that it's kind of cool how the mind just keeps doing that.
I think the more we get stressed by the world around us, the more we try to escape the world by going into our thoughts; which is fine but it means that we're trying harder than usual to believe that our thoughts are actually real. Which is fine and all when the thoughts are ones that we like, but not fine when they start to become the things that scare us. And the scariest thoughts of all, by far if you ask me, are the ones that are telling us stuff about ourselves.. "I'm crazy.. I'm a such and such..". Or "There's clearly something wrong with me..I'm a bad person.."
But in fact those are themselves just thoughts again. They're not "us". Just pictures and words (scary ones, terrifying ones even) and the moment we stop believing them to be true, to have any importance at all, they have no choice but to dissipate away. Leaving us back where we always were, sitting on the chair etc..
To take it one last step further (I don't know if any of this resonates for you at all..) I'd suggest that every time you get faced with some particularly scary thought, whatever it might be, and you stare at it for a bit and then simply let it go, well you've not only survived a sort of challenge, you will afterwards have grown just a tiny bit stronger. Like someone who's just jousted with something scary and won. So in a very real sense, in times when things seem particularly bad, it is likely that our minds are in fact sending us exactly what we need right now--tough challenges in the form of thoughts that strike down into our own deepest fears about who we are and aren't... so we feel like we're fighting for our lives, but at the same time it's the kind of fight that makes you wiser about life every single time you win, about what truly is, and what actually isn't. Stuff to make us grow into something even more than we've been before. Which means you can almost, just almost.. start to welcome some of those tougher thoughts just now and then.. like a buddy that's back to mock-battle you again, but who actually never posed any danger at all, could never have touched the real you at all.
Hope it goes well, and besta luck, Chilly.