This sounds very similar to my problem when I drink.
I also have PTSD and deal with very similar issues. For me, when I drink I have less anxiety, my depression lifts mildly and I can feel a certain sense of what I call "false happiness".
Both issues will get you to a place where you don't want to be.
I guess, those of us who suffer from this crap just need to find a healthier way of dealing. I don't know what that would be but its my estimate.
Good luck.