The max pressure should be written on the tire's sidewall. If you haven't felt it sluggish or squirming at low speeds, then your tire should be quite well inflated. If the tire is inflated over its min pressure, and it seems that it is, then there's really little chance that it will come off.
A normal pressure for a 32C tire is around 4.5 to 5.5 bars or 65 to 80 psi for an avg weight person on an unloaded bike, usually, there's no reason to go above that. (If you weigh over 80-90kg, then you can go a bit higher)
Option #1: Your hub is loose (or your spokes are not tensioned well, but this is not likely). Your rear wheel should not have any side to side movement, other than a small flex from the spokes. Some wheels are more flexy than others, but you shouldn't feel any play in the hub. If there's play, then it's the best to take it to your LBS.
Option #2: Probably you corner so fast/hard, that your tire does not have enough grip on that given road surface and you're sliding a bit as you hit the limits of the tire.
Option #3: Your tire is one that squirms that much even at the right pressures. You should not over inflate your tire because of this as it will decrease the grip, comfort and over a point even rolling resistance. You have to find the sweet spot that works the best for you. Also note, that a tire inflated over its max pressure is not safe and I wouldn't run any tire near to its max pressure, if there isn't a good reason, like carrying a heavy load or being really over weight.