My family actually immigrated to Massachusetts around 1730, then worked its way to Brookline, New Hampshire. My ancestor Frederick moved to Michigan around 1840, and that's where I was born. My move to North Carolina is very recent.
When referencing Jamaica, are you referring to black Douglas in terms of race/ethnicity or "Black Douglas" as in the "House of Douglas?"
I'm only familiar with color-coated Douglas families in terms of the Black Douglas (Earls of Douglas) and the Red Douglas (Earls of Angus).
In terms of the anglophone Caribbean, my mother is from the Bahamas, and I'm familiar with residents there who carry the surname Douglas. A generation ago, they were almost exclusively from Rum Cay or Ragged Island.
Since my dad is a white Douglass descended from Samuel Douglass of Scotland who came over to the U.S. fairly early in the 1700s, I've never had to give much consideration to people with the surname Douglas in the Bahamas or Jamaica. I never assumed a genetic relationship with them, at least not through my father's line.
The more information you can give about the people you mention, the more chance there is of someone else connecting with your family.
Dates and places of births, deaths and marriages all help to place families.
Professions also help.
'My great-grandmother mother was a Douglas from Montrose' does not give many clues to follow up! But a bit of flesh on the bones makes further research possible. But if we are told who she married, what his profession was and where the children were baptised, then we can get to work.
Maybe it is time to update the information in your profile?