regex complicated sceario during the text of markdown

regex complicated sceario during the text of markdown

Given a Markdown source text:
- sometext
- sometext
followingText
- sometext
- sometext
- sometext
I want to replace double newlines \n\n to \nWhiteSpace\n among the List
range;
so with $1 technique of JS, I did
(- [\s\S]+?)(?:\n\n(?=\n))|(- [\s\S]+?)(?:\n\n(?=- ))
http://regex101.com/r/hO7vT9
The blue selection is the target where almost working, except the very
first double newlines are failed to be selected.
This is because (- [\s\S]+?)(?:\n\n(?=\n)) matches first and the (-
[\s\S]+?)(?:\n\n(?=- )) is not evaluated.
Sure, I can revert the order (- [\s\S]+?)(?:\n\n(?=- ))|(-
[\s\S]+?)(?:\n\n(?=\n)), then now
http://regex101.com/r/tR8sN4
Now, the first selection works, but the second selection failes.(compare
to the first version, the intended result for the second selection).
Is there any work-around for this?
Of course, you may suggest separate the regex, and replace twice; well I
did, and the result is messy, so I would like achieve this in a single
regex. The language is JS.