The first thing to keep in mind is that if you were really suffering delusion or schizophrenia or even beginning to show signs, you would not be questioning your thoughts, you would believe them.
Did you speak to your doctor before coming off your meds? It might be a good idea to see them and talk about whats been happening.
I am similar to you, I can't even take simple pain killers for fear that something will change my mental state. I'm terrified of losing my mind.
I know the idea of paracetamol changing my mind is ridiculous, but yet just taking that still causes me anxiety.
I went through a really bad patch just over a year ago. I was terrified to go and see a psychologist because I thought that unless someone has had these thoughts for themselves or been through at least something similar, how could they possibly understand whats going on in my head?
The thing to realise about psychologists (and I would recommend a clinical psychologist over a psychiatrist) is that there is nothing you could possibly tell them that would shock them or make them think badly of you. I can almost guarantee that anything you say, they've heard worse. Anything you think, they could tell you a more unbelievable story (not that they will).
Another thing I realised as I spoke to my psych was that she didn't have to understand how I got to these thoughts. She didn't need to understand why I was worried, all she had to do was work with ME to find the answer and then help me to work on a solution together.
CBT is hugely beneficial. Sometimes I would get the exercises to try and think "how is this going to help" but as long as you are honest (with yourself and your psych) then it really does help.
The most important thing when you speak to someone is just to be honest, you will only get out of it what you put in.