If the cord cutting isn’t enough, try treating it like a curse and do an unhexing. The aim is to remove all links between you, then the thoughts will stop naturally, and you’ll even wonder what was so interesting.
Also watch out for parasites that attach to this and feed on it, also perpetuating it like they were farming you.
I don’t envy you, I had this last year and I knew what was happening, and it still took me 4 months and several workings targeting all levels of my being to get to the point where there was no more fuel and it started to wear off. It was 9 months until I was myself again, and I still had the odd annoying thought though, with no more emotion behind it, just habit.
The first thing I did though, was remove the pain aspect. To do that, employ alchemical transformation to the yearning, intentionally and consciously transforming it into unconditional love and allowing. It’s a lightworker technique for transforming low vibrations. Since the transformed energy is light and rarefied, and a bit impersonal and detached, it’s much easier to carry indefinitely.
For more detachment invoke the strength of Aquarius or work with Uranus. Uranus and Pluto together work well to kill romantic love as well.
A nasty case of unrequited love nearly killed me 25 years ago… after a year I was suicidal and I didn’t deal with it well, and I’d never let it go of it all this time, I just blocked it out, and with it blocked all love period… Well I was forced to face it last year, I gave up the block, immediately fell for someone and had no idea how to handle it. I had to learn the whole alien landscape and how to fix it and stay healthy. So that’s where this comes from. I feel for you, hope it gets better soon.