How do I cope with my boyfriend's bi-polar

I love my boyfriend so much, but his bi-polar behaviours have started to affect me and the strength of our relationship. He has a history of sever mental illness in his family, and I have always been thoroughly supportive and willing to educate myself about how he may be struggling. However- I can't be a superwoman, and his fluctuating mood swings are making me self conscious, worried about his wellbeing and ultimately wondering if he needs more intense help than what I can give him. He has trust issues anyway, and his questioning of me makes me feel guilty even when I have done nothing wrong. I love him and want to stay with him, but are there any methods to dealing with people like this successfully? I usually just tell him I love him when he is moody with me and don't tell him how much it upsets me. Is there more I can do?