Your bike has a conventional threaded bottom bracket (square taper). Since its a relatively new bike, it shipped with a sealed (*) bottom bracket. So, the only maintenance that can be done is tightening the bottom bracket cups (which hold the bottom bracket in place) and replacing the bottom bracket itself (which is a sealed unit containing the bearings, axle, etc.
So, the lube you're squirting is just helping your head. You may have a loose bottom bracket cup which you can tighten by removing the crank arms and then using a bottom bracket tool to tighten them up. But otherwise, the only other maintenance that can be done is replacing the bottom bracket.
That being said, bicycles are notorious for having creaking seem to come from one area but its really coming from another (since bicycles are hollow tubes, they transmit sound in weird ways). My guess (unencumbered by the thought process) is if the creaking is coming from near the bottom bracket area, I'd start by looking at the crankset (chainring bolts, crank arms, pedals) and then the saddle/seatpost. There are lots of good pages on diagnosing creaks (and this). And some bottom brackets just creak even if they're working fine.
(*) Sealed bearings don't mean that they're operating completely sealed away from the environment -- details are given in this article by John Allen. But this point doesn't really matter in this case.