Confused

Ive been married to my hubby for 14 years. 2 years ago he was diagnosed with bipolar 2. He religiously takes his meds but he gets so severely depressed he wont get off the couch. This can last for a week straight! He is nice for about 4 days, then can become nasty. I cant handle it anymore. I pray and pray but get nothing. I know divorce isnt an option. I feel so alone.