My scar's nearly invisible too - and it's a freshie, but that's beside the point.

I got no stretchies with DD1 and back to normal after the baby weight came off. I only gained 8kg with her. Went straight back into my work pants and utility belt.
LOTS of stretchies with DS but he was a whole kilo heavier than the girls. Another 8kg. Again, same as above. Skin went straight back, just with extra patterns
No stretchies again with DD2, but I did gain more than 20kgs. This time it feels like it's taking longer, but there was far more (like 3x) weight to lose. I have a slight sag over my scar, but my core is strong, so I suspect the skin is having a rest lol

Actually maybe the scar is relevant. You can't see any of my stretchies from DS, I know they can't go away completely but they aren't visible and they were never red. So maybe it is how well your skin heals?