Bipolar or Borderline?

I hope some of you can help me. My ex-husband was diagnosed as having BP2 almost 2 years ago ( he had had a major breakdown at that time)...he never went on the medication because he said he was not sick.

My ex was a mild mannered guy, never yelled and rarely raised his voice to me. He was however extremely neglectful and had an unnatural obsession with paintball (this has gotten much worse).

The problem is that he is now a screaming bully. I still have to deal with him because of our children but i can not take his rapid mood swings (he tries to be sweet but if i say something he does no agree with he flies into a rage)

He is seeing a new therapist and she has said that he may have been misdiagnosed ...that really he exhibits all the signs of borderline personality disorder.

I don't think he has mentioned to her that he is not on his meds. I do not understand how a person can be so "sweet" for 45 years and then suddenly be has BPD. He never self harmed and he sure did not have abandonment issues.

Can someone please tell me, ...what is the difference between BPD and bipolar disorder. How can you tell the differnce between the 2??