I will be able to comment on the first part of your question.
Yes low
vitamin d is an issue of concern. You should preferably look closely at your diet, and also try to get some sunshine.
Any good physician will be able to give you a supplement for vitamin d boosting. In your case I suggest to start soon.
Also make dietary changes - milk based products.
Sorry but the second part of your question of BORDER QUESTION OF CBT & psychosis isn’t very clear in itself.
Next Steps
See a general physician
Health Tips
Begin dietary changes and also start supplement in form of multivitamin after consulting with physician