Hi,
The burning you are feeling, if you have PTSD, is the feeling of the shot of adrenalin you get from being triggered. I first distinguished this feeling in light of thinking about heights. If I imagine being on a tall building, I get that burning.
I can't imagine that, physically, it would be unhealthy... I can see how it would burn off the adrenalin, serve to release anxiety for the moment.
The problem really becomes, is your need to masterbate, a reaction to the reason you are triggered.
Having been sexually abused, I found myself reinforcing negative thoughts, by masterbating to unhealthy fantasies.
The abuse made me familiar, and used to unhealthy sexual activity. I did not know it was unhealthy, because it was all I knew.
So a trigger that you are unaware of... Burning... Masterbation. I would take a look at what you fantasize about. I would be careful not to use orgasm to reinforce something something negative.
it is hard to say, are you sleeping good?