I've been dx twice, and it's been years and I still question it. I know I have have it, but I still go through periods of thinking I am fine an just need to get it together. When a really serious mood hits though, no denying it, I do have bipolar. I think a lot of us do this.

Maybe if you do write down your symptoms and times you have been depressed or manic. It might look a little clearer on paper. People do get misdiagnosed, but if you have clear manic or hypomanic periods, well then it's likely not just depression.