8 month old not napping longer than 20 mins

It’s really frustrating me. He won’t stay as well for longer than 20 minutes so I have no time for myself. No time to shower, eat, nothing. The worst part is I know he’s still tired because when I get him up he’s crabby until his next nap. I can’t take him out because he will fall asleep in the car for 10 minutes then start crying because he’s still tired. It ruins our nighttime sleep because I have to give him a nap around 4:30 or he’s just not happy. We’re both not happy anymore, I cry everyday because it feels so debilitating. I just can’t do this anymore 😭😭