If your psychiatrist has been seeing you awhile they probably have seen you in different mood states. If you're unsure, ask them for their reasoning behind it. Also, the line between being human and disorder isn't exactly clear, it depends on how something is interfering in your life. Are mood episodes preventing you from doing things you're supposed to, or want to, or make it really difficult, etc. Does it bother you, or cause issues in other areas of your life, even if you're not aware of them (relationships, finances, etc) When you're diagnosed with a disorder you usually need to meet some sort of criteria in the DSM.

I hope you're able to find some clarity, there's nothing wrong with getting a second opinion too if you ever feel it's needed.