I was diagnosed 12 years ago with Bipolar.

I recommend introducing a 0-10 scale of "how do you feel". "5" is "everything is just fine, not good or bad". upwards goes into hypomania and down goes into depression.

As BP2 he may ride at "4" a lot. You need to know if he slips down to "3", that's when he needs to get to the doctor for special attention.

The number scale helps because it takes away the shame and guilt we Bipolar types have about our emotions. Someone says "how are you" and we think we are supposed to be at a 5 or a 6 but we feel 3 or 4 and we don't want to say, "oh god, I am just barely hanging in there..." but if you know what the numbers means, it can take a weight off. IF he is not feeling well then the numbers can tell you he might need some time alone or he might want to be with you, but watching a movie or something. The numbers can tell you if he is unable to go out and socialize.

Please know that his moods don't have anything to do with you. Well, maybe some do, but for the most part the Bipolar stuff just happens on its own and the person cannot control it as much as he or she would love to be able to. It sucks to be Bipolar and it sucks to have to be Bipolar in front of someone you love. It's a hard road, and he is very lucky to have you.

Be sure to make time for yourself.
You can also use the number scale to tell him about how you are feeling. And you can use it for anything really ("that movie was a 4")-- this can be fun, just number everything