If it makes you feel any better, my old therapist refused to believe I had periods of depression. She said to me, "Nope, I don't see you as being bipolar. You don't get depression. You're just ADHD and frustrated." Meanwhile, I had constant thoughts of wanting to end my life and I had severe anhedonia.

I think some therapists try to play "doctor". They think because they see you all the time that they're qualified to make a diagnosis. While it's true they do have experience treating a variety of patients, it doesn't mean they're experienced in diagnosing people.

I solved the problem by getting a new therapist, one who listens to me and believes the bipolar diagnosis. My old therapist had a MA in Psychology, but my new therapist has a PhD and is a psychologist by training. Unlike her, he can technically make diagnoses, but he doesn't try to diagnose me. Instead, he talks to my pdoc any time he has concerns. They work together, and I think that's the key.

While it may cost you money to switch therapists, I think it might be worth it in this case if you can afford it!