Start over and do NO quests. Until you hit lvl 40 or so. Just explore, kill stuff, gather pelts/ingredients/ore, craft it into things of higher value.
I'm thinking of starting over (again), and not even entering any dungeon (aside from Bleak Falls Barrow or Ustengrav) until i'm lvl 45 or so.
...Because I have the opposite problem. I have tons of quests still to do, but I've level-locked most of Skyrim's dungeons at whatever I first explored them at. It's not much fun at lvl 30 to get a quest to "Kill the leader of Gloombound Mine" and find the sorry sap wielding an iron battle axe and wearing pelts.
This 600%. Try using a challenging race/class mix (like an Orc Mage who specializes in light armor/pure magic instead of heavy armor/fighter). Or just try taking a different approach to the game that involves more character building and less achievement/questing. That's all I did up to lvl 45 or so---nothing but open sand box by just letting my Battle mage Nord live off the land. The initial goal was to build a fighting/magic skill set in preparation for the MQ. I did this by 1) making a mini game of building up a profitable blacksmith business early in the game and 2) run the smith from owning at least one house. The house would be also used to store all the additional junk I'd get from the upcoming quest lines (like becoming the TG and DB master). After completing the TG/DB quests, my focus shifted to improving my magic ability by doing the harder Daedric/Dragon Priest and other faction quests. Then start the final preparation for the MQ by acquiring all the houses through doing the various side/miscellaneous/favor quests.
So I basically started out from lvl 1 by exploring and putting locations on the map (with NO dungeon raiding or exploring towns to get quests) by literally sneaking everywhere up to level 45. I'd use my bow to do sneak attacks to avoid open conflict if I couldn't sneak past trouble on the roads etc. This built up my sneak/archery skills really fast. On the way, I acquired or found magic clothing which enhanced these skills.
Since trading pre-made items with the smith wasn't profitable, I decided the best way to make $$$ faster was to make them from scratch. So this meant I'd need a house to base my operations/store my goods etc. for sale. I settled on Riften because it's the TG HQ and a good base of operations. The Honeyside house is also the only one I know of in Skyrim which has an entrance that bypasses the guards at the hold entrances. So if you've got a bounty or not a TG member, it's a convenient way not to end up losing your loot!
Here's some stuff that I did that you might want to consider via a crafting route:1. start a new character and make a mini game of hunting/fishing for food (to cook and save food that give health/stamina bonus when fighting); hunting for animal hides (to make leather for armor/weapons); mining and smelting the ores from mines in holds and towns (to make weapons/armor).
2. Use certain world encounters to your advantage. I got adopted into the Orc clans around Skyrim so I could get access to the rare Orchalium ore in their mines. I even stole the more exotic ores/ignots from exotic locations like bandit camps and shacks/ships I ran across while exploring. I think I found some rare conundrum and moonstore ore veins from one particular giant camp in the Rift somewhere.
3. haul this loot back to a smith's forge in the nearest town or settlement. Smelt the ore into ignots, tan the hides into leather and combine these at the smith forge/workbench/grindstone to craft improved armor/weapons from leather and iron. Then reinvest the money in smith training to upgrade these weapons/armor, as well as your sneak/archery and other combat perks. As my smithing skill got better, I upgraded to making steel/plate. I also started raiding the Dwemer ruins for dwemer artifacts to make dwemer armor (there's also a Mage that will pay $$$ for these as well after doing a certain quest, so don't smelt everything you find into ignots!). I also began working on my enchanting skill and upgraded to the arcane enchantment perk at the first opportunity.
The combination of using the smithing to improve armor, then enchanting them, allowed me to craft some extremely valuable weapons and armor from scratch.
I then sold these to the smiths and town vendors for $$$$. 4. Make a minigame out of collecting all the armor and weapon sets and decorating all of your homes with them--especially the ones in Solitude and Windhelm. You get a bonus to your armor if you're wearing a complete set btw. In particular, the Dwarven, Dragon and Daedric weapon sets are some of the hardest to come by in the game. This is because of the more dangerous enemies you'll likely have to defeat in order to acquire them.
5. Make a mini game out of seeing how many rich spouse NPCs you can marry in the game (both male and female). Explore your creativity an discover innovative, Machiavellian ways of hooking them up on dates with Sithis. Then marry the next spouse. Rinse and repeat.