Hello Person: I see this is your first post, here on PC. So... welcome to PsychCentral!
I hope you find PC to be of benefit.
One other forum, here on PC, you may find to be of interest would be the spiritual support forum. Here's a link:
https://forums.psychcentral.com/sanc...itual-support/
I'm sorry I cannot tell you whether or not what you are expeiencing would constitute PTSD from leaving your religion. I think this is something you would have to explore with the help of a skilled counselor or therapist. Anything I would suggest would be simply a guess based on very little information.
It's difficult for me to relate to what you have experienced since I've never had any religion. The closest I come is that I have been a student of the writings of the American Buddhist nun Pema Chödrön. Pema teaches the ancient Tibetan Buddhist discipline called "Lojong" or "mind training". And one of the primary precepts of Lojong (as well as with Buddhism in general I would surmise) is that we must learn to be comfortable with uncertainty. Ultimately, there is no firm ground... nothing to hang onto... no sanctuary... if you will.
One of Ani Pema's original teachers, the late Chogyam Trungpa, has been quoted as having said: "Chaos should be regarded as very good news." This is because he understood that we learn & grow the most when we are challenged, not when we imagine we have everything sewn up. So, from that perspective, perhaps the challenge for you is to find a way to use your loss of faith in Islam as a vehicle for advancing yourself as a spiritual person. I don't know. But these are my thoughts on the subject.
There is such a thing as existential depression. Perhaps you've heard of it? PyschCentral's archives contain some articles on the subject. Here are links to 5 of these:
https://psychcentral.com/lib/what-is...al-depression/
https://psychcentral.com/blog/coping...dium=popular17
https://psychcentral.com/blog/existe...human-anxiety/
https://blogs.psychcentral.com/nlp/2...dium=popular17
https://blogs.psychcentral.com/good-...omment-page-1/
My best wishes to you...
