Well believe the problem is with your drill bits and drill itself. Also if you are trying to drill a big hole might be good to first drill a small one and then use a bit with a flat bottom (not sure what you call that shit). Also aren't you supposed to use a slower speed to drill wood?
usually pilot hole(drilling small hole first) is a way to increase the accuracy, usually this works for harder material and more dense wood. This is a very common practice when drilling into steel, but works for wood as well.
Drilling speed depend on various factors, mostly depend on the material and drill bit.
for twist drill bits, higher speed works better for wood and alluminum, slower speed/higher torque works fro mild steel
for bits like auger bits, it is better to use lower speed and higher torque, but higher speed low torque is best for spade bits and speedbore
Older bits like auger bits were designed to use in hand driven drills(Bit brace and egg beater drills), so those were designed to use at lower speed.
Modern drill bits (twist, spade, twist and whatnot) are designed to use in modern power drills with relatively higher speed.
Actually, there is nothing called drill bits, it is the drill(we call it drill bit) and the device you use to rotate the drill is "drill driver"(we call it drill)
