I want you to ask your Therapist how HE suggests that you let the past go and see what he says. Ask him for some "tricks" or what HE would do to let go. Ask him how you stop it from playing over and over in your head. Lets just see what HIS suggestions are!
I do agree that you need to talk with your doctor about the medication -- you may need an increase in dosage or an actual switch to something else! Sometimes these meds or the combination of the meds just don't work. Trying something else might.
I wish you the very best! God bless & let us know what HIS suggestions are. LOL Hugs, Lee