has he ever asked how he can help, or have you ever outright told him?
Education about it is the key 🔑. I do have Bipolar, too. My husband just asked me: Do you want to talk or let it go for now? Because I get tired to back and forth the same issue over and over again. Normally, I say, I'm in that sad episode, I will be fine, nothing personal, I will handle it. Or, if I am still overthinking, I bring the conversation out in the moment when we are alone without distractions, and he can pay attention to me. He just listens and gives me some opinions. If he thinks he should, sometimes he just listens, and that is enough for me, then I feel better. This condition is very hard, but he should know that you are on one of the episodes and he understands. But he should read about it.
Maybe ask him to look into it a bit more so he can support you more. It's not easy for either of you mostly when he doesn't fully understand. I've only recently known about bipolar is I'm doing a course if I didn't do that I wouldn't of known anything about it. Its good that he's trying at least! A lot of people wouldn't bother so I'm sure he will be more then happy to look into ways to help or help you cope with it.