Hi Diva, there is obviously a trigger there that sets you off. Is it your Mom (and I don't mean that in a bad way), maybe the room you were in, the music, time of the season...I know it could even be the music for me which would remind me of a trigger. Can you remember a smell that was happening at that time, maybe your Mom was cooking also at that time, maybe it was the security you felt with her dancing in the room, very carefree and this triggered you when you went walking with your husband.
I'm just trying to remember my EMDR session when my counsellor would try and set the mood for my triggers. She would ask me what time of day it was, what season it was, was there any smells that stood out, who was there with you, where were you, any particular clothing, or colours of fabric that stood out, any detail at all to help set up the "mood"...maybe that would help you out to try and figure out what your trigger was.
I hope this helps a bit.