The game has a lot more to offer then just dungeon crawling, and maybe that's your problem. You didn't really state what you've completed. There is an entire world to explore, books to read, people to talk too, tradeskills to mess around with, and god knows what else.
Perhaps try with your next char to a) not rush,

use "useless" perks, or c) read into the culture a bit more.
Honestly, I can spend hours just reading through all the books, talking to towns people and organizing the crap in my house (yeah, I'm a bit OCD about where everything is). Sometimes, I don't even get to go out and quest. I wish I could setup shop and sell my crap all day long, yeah be a bit simcity-ish I guess, but would be cool nonetheless.
You could rp too, I do that a bit, but nothing major or in-depth. My wife just thinks I'm "thinking out loud". Might want to try and curb your playtime too. Maybe you just playing for too much at a time, and not able to enjoy it nearly as much. Remember, absence makes the heart grow fonder, and it works for Skyrim too.