Should I get a second opinion about my friend's condition based on his behavior?

I am a caregiver for an 83yr old gentleman who is residing with me. We have been roommates for 15 yr. I pay half the bills, so does he. I know it sounds like a weird relationship, but it has worked for both of us. About three years ago he had Aortic Valve replacement surgery. His mental status started to go down hill since then. His doctor has diagnosed him with Dementia and has tried him on a number of medications, all of which he has had side effects. He is not on anything now. I am at my wits end because I know some of the things he does are Dementia related but some are an act to get my attention. He shuffles his feet and takes 5 minutes to get around the kitchen and makes sure I am watching. He also sniffs (like his nose is running) just to upset me. He does not like my friends and always makes very bad comments about them. I can't go anywhere without him calling me and telling me it is time to come home. Do I need another opinion on how ill he really is? We go through this everyday.