Hi Ed,
I think you should be very proud of yourself for leaving a toxic relationship, it isn’t easy to do especially when the person used to be someone you really liked. I hope therapy is helping you with your ptsd and depression. I think it is completely natural to be upset over your breakup even though the relationship was toxic, she is still someone who you used to be close to and I’m assuming a big part of your life.
Here is some advice feel free to adjust depending on what you would think works for you and just ignore the advice that doesn’t. I think that maybe try to replace the time you spent with your ex on being with friends or your support network. You could also develop on any hobbies that interest you so that you can get your mind off of thinking about your ex. I also think that maybe as soon as you notice yourself ruminating in self hatred try to recognize those things as thinking and thereafter try to refocus your attention on what you were doing before the rumination. You can also redirect your self hatred and come up with three good qualities about yourself this can be about how you are towards other people or the skills you have etc. Usually when I experience self hatred I use meditation to refocus my energy and especially guided ones can be helpful. Remember that you are not your thoughts or feelings and automatic thoughts have been created based on our experiences and if we have had a lot of bad ones then they can tend to lead to thoughts of self hatred. I feel like I’m making a lot of statements and I want to preface all of this by saying I’m no professional and these are suggestions are based on my beliefs, philosophies and experiences. I hope some of it helps.