NavyGunns is right, it’s the multi-tasking, and the not knowing when it will ever end. When I was a caregiver to my elderly FIL, who had significant issues, it was like I had nothing for myself. Everything revolved around him.
Everything didn’t REALLY revolve around him, of course. It was that I let everything revolve around him, even that I insisted on it. The caregiver puts more pressure on himself than the patient does. So what he needs from you (and from himself) is permission.
Yes, tell him to chill.

You’ve got this. You’re getting better every day. He needs some “him time.” Tell him to go to a movie with friends or family members, or alone if he chooses. Or plan a two-of-you-together afternoon or evening of watching movies or shows at home. Bowling. Golf. Attending that air show that makes him perk up whenever he sees it on the news.
When I told Mr. Shoes I was feeling trapped by Dad and like I couldn’t do any “me” things, like go to a convention in Kansas City with my best friend and fellow author, he said, “Then go. We’ll work it out.” And they did. And I went. And it helped.
When we get overwhelmed, and we all do at times, it helps so much to take a deep breath and do something normal to remind ourselves that our regular lives aren’t gone, just waiting around the corner.