BestFriend2, welcome to the board. I am sorry that you need to be here but glad you found us.
What you described does sound as if he does have cognitive problems. It is difficult to say what it is with a proper diagnosis. It could be side effect of one or several of the medications he is on. It could be so many things... or it could be one of the many forms of dementia. It is best that you do get him a diagnosis.
I am sure that he goes to the doctor with all his medical problems. What you need to do is to talk to the doctor BEFORE he goes to the doctor the next time. Explain to them that you have become aware of cognitive decline and ask them to do a MMSE (Mini Mental Status Exam) at the next visit. He doesn't even need to know that you talked to them. That simple 30 question test will give indication of the cognitive decline and hopefully they will recommend test and follow up to find out what is going on. Let the doctor be the bad guy!!! He should get a complete physical including blood work, a complete review of all his medications for side effects, and a CT or MRI. They will probably check his carotid (neck) arteries for blockage which can cause cognition problems because of poor blood flow to the brain. They will rule out all other causes for the cognitive decline that can be fixed and then make the necessary diagnosis. It is so much better to know what you are dealing with, fix it if you can, and then know what the future will be. Not knowing and worrying is often worse than knowing.
I do hope you can get him to the doctor and find out what is going on. Let us know how it goes and what you find out.... We are also here just to listen if you need to vent