Negative loop

So, sometimes i have these negative thoughts about my bf.
And in that moment its really hard for to not get down that road.
My brain has gotten so good.

So i guess my question is on how i can stop going down that road in the first place?
Push them aside an focus on another thought?
Should i just let go of these negative thoughts.
Because my brain is like: i can proof that he isnt the one. And then lists all of the facts.

Will these doubtful thought ever go away?

Thanks for your help!