My first therapist said "not bipolar" after a few sessions. I was thinking, "lady, do you think you even know me after a few sessions?" She even had the audacity to say I've never experienced depression, and implied that I didn't know what depression was. Liar.

My current therapist said she's seen me manic a couple of times, and she's been seeing me for a year now. I didn't have a manic episode until about the 12th session with her (I see her weekly). She just needed time to assess me, as IMO she can't assess me after only a few sessions. That's b_llshit.

Btw, I keep going on/off meds, so I have episodes frequently (because I'm an idiot).

So based on my experience, I would say that your therapist should NOT be diagnosing you after 3 sessions. She's either inexperienced or doesn't know what she's doing. (Sorry, but I really think your therapist doesn't know what she's doing if she thinks it's ok to diagnose a mood disorder after only 3 sessions.) Mood disorders need time to show themselves.