In love with my boyfriends cousin.?

Well ive been with my boyfriend for about 4 years aand i absolutely loved him until he became bipolar. Me and his cousin will allways be there to help him and one day my boyfriend went crazyyyy he was runing after me to hit me than his cousin came and piked me up to take me home he told my boyfriend to take his medicine and wait for him to come back. While we where in the car and i was crying he help my hand and he just kissed me and told me he loves me. He has the most beautiful blue eyes i have ever seen in my life and hes just georgous personality and looks but what do we do about my boyfriend it is so sad PLEASE help