I think there have been some excellent comments here.

Something that makes, to me, your previous psychiatrist suspect is the diagnosis of ultraridian (sp?) cycling. This is a controversial diagnosis, there are a lot of pdocs who disagree with its validity.

As someone pointed out, if you're jumping from one emotion to another during a given day, and especially if these emotions are triggered by relational interactions, this is indicative of BPD. Bipolar episodes are persistent 'moods' over a period of time, whereas BPD revolves around 'emotional' instability.

Yes, you can be impulsive if you have BP and if you have BPD, but I think the difference is what triggers this.

You have mentioned before issues with rage. My brother has BPD and has extensive issues with controlling anger. He's explosive. This can happen in the context of Bipolar Disorder, but again, it depends on the context (again, relational and emotional instability in the case of BPD). I also find it telling that Bipolar meds have been of little help, in controlling rages, or otherwise.

As Nammu said, the great thing about BPD is that it is curable. DBT has had excellent results (wow, I wish my brother would do it, but he denies the diagnosis, to his and his loved ones' detriment). And you don't need Bipolar meds with all of their side effects and in some cases, still unknown long term effects. So there really is an upside to the change in diagnosis, though I understand why you may not feel that way right now. It's a bit of a whiplash to suddenly find yourself with a different diagnosis. But if it fits, you can really do something about it, and that's gold.

Please stay on PC, there is so much support here!