I've done thieves guild, about half of the companions, and am finishing up the stormcloaks. I feel like I'm going to run out of quests to do soon Does anyone else feel this way? Like they're gonna do everything too fast?

The guilds aren't the only quests you can do.

I've completed the Companions, Legion, and Winterhold, and almost the main quest. I still feel like I'm not even 10% done with this game.

I though the same way, but then I realized I hadn't stopped playing since Friday afternoon.

I've logged a good day by now and I've just barely completed half of the main quest and all of the college of Winterhold, excluding the side quests you get from their members. I have no idea how you guys are so efficient!

There are so my quests outside of the main and secondary lines that it's not funny. They fall under the miscellaneous quests and are generally "found" by listening to conversations or talking to lots of everyday people.

not only misc. you can get named sidequest by enteriung dungeons, reading books, talking to people etc.

Thank you guys

Congratulations, you've MAYBE scratched the surface

You haven't even touched the surface my friend, or maybe that's all you've touched. Either way there are so many hidden quests in this game it's amazing, and I love it. And they way quests are found and discovered is an amazing achievement Bethesda has done all in it's self.