Is there a way to help my bipolar boyfriend?

Support his therapy: If he is not in therapy, encourage him to find a good one that he can trust. If he is, encourage him to use it to it's best advantage or find a better fit. Be compassionate when he feels bad, but don't enable bad behavior by making or accepting excuses. Firm, caring consistent support is all you can do - do not try to be the therapist. It's difficult even with training & experience.

He has to want it: Your boyfriend has to want therapy and medication, and all you can really do is encourage him to seek both and engage deeply and meaningfully in the therapeutic process. You simply cannot do it for him, much as you'd like to. You can either be his girlfriend or his therapist. You cannot be both, and even though you want to see him get better, trying to be both simply will not work.