Its the mania that makes you think like that. I get to thinking while manic, and convince myself my boyfriends cheating... Try to keep yourself in the mindset that he married YOU for a reason. If he wanted someone else he wouldnt have married you!

Plus, I know nothing about your situation... but be glad he supports this angry disease we have. Its hard to find someone who will stand by you through tough times like this... Since he is, please try and relax those thoughts. He obviously loves you, and isnt going anywhere... Manic or not