I too go through that cycle of belief/disbelief. It's like when I start disbelieving that I'm bipolar, any memory of it disappears. The hospital visit, the manic episodes, the suicide attempts, the whole thing just fades away and I'm convinced that it was all just a big misunderstanding. Even today I still have that little thought in the back of my mind that it's not real. I think that all falls under the title of "delusions".