LT-
FWIW I have to say I agree with zoiecat. A group would be a commitment for sure, but you could see life changing benefits.
It doesn't seem you've made any progress with Dr. T in the area of healthy emotional regulation and ability to sit with your feelings. Those hard feelings will always come and go for all of us. We are just human. And sure, we need support from others- but as adults if we can't sit with our own painful feelings and begin to metabolize them in the moment we will always truly struggle.
Dr. T has potentially hindered your ability to sit with hard feelings by seeing you three times a week for years. You have become dependent and feel terrified of sitting with hard feelings on your own. This is potentially very harmful to you and will get worse without some intervention. Much like a drug dependence (and constant validation/comfort is a drug as far as the brain is concerned) you will have to struggle to get back on your own two feet but you can do it.
Therapeutic support is one thing. But a competent and supportive therapist knows when to gently step back and encourage a client to have more autonomy and independence. Dr. T appears to do the opposite. Have you ever researched DPD
Dependent Personality Disorder (DPD) - Dependent Personality Disorder (DPD) - Merck Manual Professional Edition Does this resonate?
Do you feel Dr. has encouraged you to truly increase your tolerance threshold?? IMO If he had I think the HE would encourage you to titrate down on sessions. HE would strongly encourage a DBT group. Sure, it would be hard at first but as a therapist he can support you through the transition to twice or once a week. He could support you in attending a group. That's literally his job. But he doesn't seem interested in doing it. Ask yourself why. And remember that he profits financially from your unusually high session frequency. I'm not suggesting that is his conscious motivation, but it's something to keep in mind.
Who is truly benefitting from this set up of 3 times a week for over 4 years?? You or him? If you stay with him you may have to really advocate for yourself by telling him you think you may need to reduce sessions and you know it will be hard because you've now grown very dependent.
Edited to add- this is obv just my own opinion and if none of it resonates with you then please disregard. But listen to your gut and ask yourself some hard questions. Advocate for yourself the same way you advocate for your child- even when it's challenging and requires making changes.