I fish almost four days a week from the same dock and can't catch anything. Maybe there just aren't any fish there.

Just so you know, they are ALWAYS on the "other" dock.

I feel your pain.

Most likely out deep in the wintering hole. Might not get any dock action for a while depending on how north you are

what are you throwing?

I've tried a lot of stuff. Slow rolling spinnerbaits. Shakey head. Skirted jigs with rage craw trailers. Deep crank baits. This dock is on a large River that only gets about 25 ft deep in the channel. Where I'm fishing it's from the bank to 15 feet deep.

try suspending jerkbaits. another potentially useful technique that i didn't see you mention, is dropshotting. i.e. a robo worm on a dropshot hook, fished off the bottom.

Shakyhead with a grub or small jig

Just sitting on a dock and casting around is probably not going to be your best bet in winter. If you usually catch a lot of fish there, then your presentation is probably off. It's hard to give a specific answer to a question without a lot of detail. Be more specific. Structure? Cover? Water clarity? What river? The more specific the better.

It is very possible that where you are fishing really doesn't have any fish right now, especially if the portion of the river you're on has current and nowhere for the fish to hide from it. 

Fish much slower. You won't get as many reaction strikes in the winter, but bass are still opportunistic feeders and will hit lures.

It's the Kanawha River in charleston West Virginia. Lots of lay downs around the dock. Some dead grass in 5 feet of water. Clarity is about 5 feet. Current is average. Rip rap on the banks. We also just had two warm sunny days, today is the third day of it. I'm going out again this afternoon to try. I figured some would come up shallow around the rocks cause it would be warm.

Slow it down till you feel like you wanna scratch your eyes out.

Like bluebasser said, if there is a good bit of current there, that could be your problem. Current in winter is not a good thing.

Any chance the river is frozen over & the ice is stopping your lures from reaching the water...?

Im fishing the inside of a turn in the river, I've heard that the outside of turns get more oxygen and food flowing over there. Could there be any truth to that?

I would just focus on the side opposite of the channel which most of the time is the inside turn. Unless you have a lot of ice on top of the water, I don't think oxygen is a big concern. The areas with no current will also hold more bait.

Slooooooooowwwwwwww down till you can't go any slower

I fish the Upper Potomac and have the same problem in the winter time.  I just can't reach the wintering holes from the bank and normally don't catch bass in the wintertime.  Are there walleyes in your river?  Maybe try a ball head jig and gulp minnow or grub.