Is it MCI or Dementia?

My Significant Other and I have been together for 29 years. For as long as I have known him, he has had a poor memory. Lately he seems to have more memory lapses - doesn’t remember even recent events. His hearing is really bad too and I don’t know if he is just ignoring me, or really can’t hear. He can’t seem to focus on more than a couple things at a time. He has a cell phone and can’t remember how to do things, even though I have shown him multiple times. This has become a very real irritant to me. He gets upset with me if I ask him if I can see his phone because I don’t know what he is doing - doesn’t explain well enough. He tells me to tell him what to do on his phone and I can’t help if he won’t let me see it. Then he tells me to just show him what to do but he doesn’t remember even if I show him. I lose patience a lot! I have days where I vow to myself that I will not be impatient, and then he does or says something that triggers me and I get upset. My tone can be pretty harsh along with my facial expressions and words. I love him but he is driving me crazy. How do I learn to cope with this?! He is 84 in April. I am 78 and I have a good memory but he accuses me of not knowing what I’m talking about. Lately I feel like may be I am losing my memory and mind. In addition to all this, he walks stooped over and says he can’t stand up because his back hurts. His feet hurt. He has neuropathy. Everyday it is a new health issue. He orders every supplement he can think of or that he reads about. Sorry for the rant but I don’t know how to deal with this. We play memory card games and he is pretty good at that if he stays focused. We play ping pong almost everyday and love doing that together. And we try to walk a little everyday. I think others have noticed his decline but I am hesitant to mention my concerns and they don’t mention it either. What can I do for him?