Yes, you have separate problems with your significant other, and of the two I think the fact that he doesn't see "lying" the way most of us do---the way you do---is your biggest problem. You can be bipolar and not be a liar, and not all liars are bipolar.

But there is definitely a connection between bipolarity and cognitive issues. Meds can also contribute to the dysfunction.

I used to be very bright and had a great memory for details. But as my BP has worsened, so has my memory, and I take two meds that can really futz with cognition as well. Only recently have I come to realize that my nursing career is basically over because I can't remember stuff, focus on a task for more than a few minutes at a time, or avoid getting distracted by the tiniest of things. My executive function essentially doesn't---I also pop off with inappropriate statements at the worst of times, and have the nerve to be surprised when everybody else is staring at me like I just sprouted three heads.

This is HARD for someone who always prided herself on being an intellectual. But that's gone and it ain't coming back, so I have to adapt my strategies to my new reality and get on with life. Your SO will have to do the same thing, and to some extension you will too if you stay with him. But again, his untruthfulness and his perspective on it are a little scary, and FWIW it's got nothing to do with his bipolar. Best of luck.