Do you still have strong feelings for this ex from 20 years ago?
It could be a sort of "trapped" feeling. Like you would LIKE to connect, but due to your marriage, her relationship, etc., you feel you can't/shouldn't.
I have an ex from the past I still have feelings for. Just never completely got over him, I guess. Mannnnny years ago I had the weirdest dream that a floppy hat was caught in the wind, circle-ing over and over in the air. It ended up caught against a picket fence, pressed flat from the wind...outside the yard of my ex's home (weird, in that he had no picket fence there - so I know what you mean about dreams. LOL ).
I told a friend about it - who is into dreams. She felt the hat represented me/my convulted feelings (guilt, confusion, etc., since I AM very happily married and DO love my husband) and getting stuck against the fence was part of the "can't go there" representation.
If you google about lost loves, there's a message board out there that focues on this dynamic. People still stuck on ex's from long ago. Maybe someone there can interpret your dream for you?
It's such a crazy feeling, isn't it?