What a read! I went through quite a similar experience and felt the same way about being embarrassed, regretful, etc. Why couldn’t have seen the red flags when they were so obvious? Unlike you though I was (still am) a new grad with limited experience, so my D-Day was an extremely shocking time that put me in denial for a good while.
For me it’s almost been a year. I spent many months dealing with the fallout; now I’m in a much better place. So, to a degree, I’m glad it had happened though it was extremely painful while it was happening and for a while afterwards.
Shout out if you want to hear my story. I don’t know if it would help you in any way to hear it though, let me know.