New Guy, but fasting for about 6 months.

Hello all,
New to this forum, but a pretty experienced faster.

I have fasted as long as 20 days in my recent past. In the last 6 months I have fasted my way down from 219 lb to ~150 of today.
I was fasting mainly for insulin reasons, so I'd eat fat and vitamins and apple cider vinegar as well as coffee and tea with heavy cream and sucralose. As well as other things that was mostly fat like mayo or just non caloric - like hot peppers and mustard.
It was very very effective as a 70lb loss in 3 months or so suggests.
The question I have is this though.
When I get to the 150lb mark my stomach feels like I am sucking it in, when I am not. What is that feeling and is it bad or something to worry about. or is it good - as in my visceral fat is getting burnt, and that lets my internal organs move a bit more and causes my muscle wall to take up that space ?

I am after reading your site - thinking of the more pure cleanse style fasts where I just take a few water soluble vitamins and water - and true black coffee or tea only. But keep it short, less than 4-5 days. I don't think I have more than 10lb spare fat at this point to do anything longer without risking some injury.

FWIW I am a 5' 9.5" 48yr old male on the border of small and medium frame. No prior health conditions - except pre-diabetes which I have now killed.

Thanks guys.
Srinath.