Just a check: he doesn't have Asperger's Syndrome, does he? I'm no expert and he isn't sounding 100% typical of AS to me, but a few red flags are popping up. If you aren't sure, it might be worth at least checking on. If nothing else, some of the same strategies that are useful for living with someone with AS might be useful for you, too.
Have you tried requiring "quiet time" for a while in the afternoon? I lived and died by that when I was worn out by all the talking. (I'm an introvert, so my alone time is a physical and psychological necessity for me!)
Have you tried finding things your son can immerse himself in alone? This may require baby steps, and he will probably resist at first, but I think you have to be firm about it. You have needs, and he's trampling on them, whether he means to or not. He sounds like an extrovert, but just as introverts have to learn how to deal with people, extroverts have to learn how to be alone.
Rather than running away to get some peace and quiet, I think you have to lay down the law. You're allowed to set limits on how he can use your time. The shower ought to be a safe zone! He's old enough to understand and respect this. Set some rules and use the carrot-and-stick if you must in order to get him to follow the rules.
Playdates with friends help, too. If he has other kids to talk to, he'll leave you alone more.
Good luck! I'm exhausted just reading about it!
