The bumps on the back of your tongue are normal, everyone has them, some are bigger than others. Mine are huge and look like giant warts, my kids crack up whenever they see them.
As for thrush, it is very distinct and is more than just a simple white coating. It is like a curdled milk coating in some spots, and when rubbed off it does indeed make a sore spot. I've had trouble with it off and on due to asthma meds. I do not know of any across the counter med for thrush, I always need a prescription for Nystatin, an antifungal that you rinse real well in your mouth and then swallow.