I'm sure there are many other people who feel like you do, OP. Being stuck at home together almost 24 hours a day due to lockdown has placed a great strain on many relationships, just as the change from working life to retired life makes some couples realise that they don't really like each other or want to spend loads of time together.
If you've been together for 50 years, I assume you were already retired before lockdown, but perhaps you both filled your days with separate activities and didn't realise until now how far your relationship had deteriorated.
Whatever your age or length of relationship, you don't have to stay together if you don't want to. Nor do you have to put up with him being irritating. Tell him calmly what annoys you, and ask him to make specific changes.
I suggest you start by building in some alone time - you are entitled to go out for exercise, shopping etc. - and if he says, "I'll come too," tell him that you've been feeling very stressed lately and want some time on your own. Don't rush into anything until you've had some advice and decided what to do.