Ditching my own plans

Diagnosed in my late 40’s with both ADHD and ASD. Diagnoses came a year or so apart. I had previously been diagnosed with anxiety, depression, PTSD, an eating disorder and too many other things to remember. It’s only been a couple of years since the ASD diagnosis. Life has gotten so much harder in ways I never could have expected. One of the things that is really troubling me is the seeming inability I have to keep any plans that I make, social or otherwise. I will happily suggest plans with my husband and then when the day comes to actually go do the thing I feel nothing but dread. Increasing anxiety, guilt, shame, fear that I will drive the people I love away. Complete relief if the plans are canceled, either by me or some other way. If the plans still happen and I go I am a total nightmare and I can’t stop myself. It’s like I’m punishing everyone and everything. It’s horrible. Is this PDA? I’ve had a therapist tell me it is but haven’t gone through any official diagnosis process. I’m pretty sure it is but any other voices telling me I’m not wrong may help me finally try to understand it better.