Thanks so much for the support you all!
It really helps knowing that I'm not the only one like this... I tend not to talk about it much because a lot of people really don't understand.
My psychologist is always telling me about these workshops he goes to about "creativity and madness" so maybe this particular sort of psychosis is fairly common amongst artistic types? I just figured modes of depression and mania were common, didn't know that a lot of people went through things so similar to what I go through!