You could also have a slight ear infection which is putting your balance off without feeling painful.

Some chemists will take your blood pressure so perhaps call a few to see if you can get that checked. I have low blood pressure and it can come on like how you've described. If that is the culprit then you need to lay down and wait for it to pass and before you stand up try squeezing you calf muscles for a few repetitions to get the blood pumping up your legs.