I'm sorry you are struggling with this. The consensus of opinion seems to be, I think, that one cannot stop thoughts. In fact, trying to stop thoughts is the surest way of ensuring they'll keep coming back over-&-over again and even strengthen. Instead what is necessary is to learn to allow them to come forth without becoming "hooked", so to speak. I've never had CBT or DBT; but I believe there are techniques for working on this that are taught in those types of programs.

Actually, the Buddhists already knew how to work with intrusive thoughts thousands of years ago. And a lot of the techniques one reads about nowadays come from Buddhist practice. There's one technique I myself am particularly fond of. It is referred to as "compassionate abiding". The technique is thoroughly explored in the writings of the Buddhist nun Pema Chödrön. However here's a link to a mental-health-oriented description of the practice:

Relieve Distress By Allowing It: Compassionate Abiding 101 | Mindset: Perspective Is Everything.

May it be of benefit.