I dont want him to love me, I want to have no feelings for him whatsoever.
I still love everyone I've ever loved. And there's sadness that those relationships didn't turn out as they might have.
I have not stopped loving them, missing them, decades later.
But I also am disciplined enough to not need to be in contact with them. I can love them, and not need them.
I don't have to change my feelings, they are what they are. I don't have to change their feelings, they are what they are.
I can change my behavior, and choose to do what is healthy and good for me.
Perhaps there is room to love yourself more than someone else, then be able to love as much as you love yourself. The WTS molds us into people that discount ourselves in favor of others, sometimes. When that happens, we start judging our worth by how others see us, and need them to need us.
It can be a long relearning process to value ourselves, and enjoy the company we keep when we are alone.
How do I banish negative thinking? the kind that keeps me awake at night.
Find something you love and immerse yourself in it. Music, books - meditation. Meditation, while listening to non-demanding music that nourishes your heart, can help you focus on your experience of existing, on what it is like to be alive and have a body in this world. Focus on what it is like to breathe, what it is like to have a heart beating.
This is "boring". There is little to occupy the mind. We are taught to use our minds all the time, and much of our sadness can come from replaying thoughts in our minds. As you mention.
If not meditation, perhaps creative visioning: use your mind to imagine a yourself doing things you would never think of doing in life. Use your imagination, occupy your mind, with visioning your future: who is there, who you are in relationship with, how youare acting, how you are feeling.
And drift off in peace...