Hi Leni - my friend is a maternity nurse and has been an invaluable help to me, especially with stuff like feeding.
Her advice is feed for an hour (maybe a little more during growth spurt weeks) but not to allow a snacking habit. He's not eating, there is no way his stomach is big enough to swallow milk for 4 hours. She told me to feed, stop and wind, feed, stop and wind etc, and after an hour if my dd was still sucking to tap her lips with a finger and see what she did. A hungry baby will grab at your finger, a vaguely hungry one will open their mouth and move their head towards it, a full baby won't really react.
After an hour and a half max, stop, whatever, you're being used for comfort not food.
My dd sucks her hand and fusses when bored, over tired, trapped wind, colic, dirty nappy etc. Hand sucking isn't just a hunger cue. She also frantically sucks on the boob when she is has trapped wind. It isn't hunger, she's uncomfortable so is looking for comfort.
You've got to stop the snacking before it becomes a habit. The best way is to go out. You are probably both bored and frustrated and the fresh air will do you both good. My really DD doesn't nap. If I stayed in she'd probably chew on me all day and I'd crack up. I put her in the sling (she kicks and cries for the first 10 minutes) and then falls asleep and will sleep for at least an hour, sometimes 2. That way I get to space her feeds out so she is properly hungry, swallows sensibly and doesn't comfort suck.
As for showering and dressing, just do it. Put ds in a moses basket or bouncy chair in the bathroom with you and shower and dress. He may shout a bit, but he will be safe and you can talk to him. Same with meals, although a sling can be better as he may well go to sleep.
It's really tough when they do this. Big hugs.