8.9 isn't very high - it's over the cut off point for the test but not by a huge amount. Generally you're looking at BSL's around 11 (which is really, really high) before you'd be getting symptoms like you're describing.
GD doesn't usually cause any symptoms unless it's really raging out of control (and even then maybe not) so I'm thinking what you're feeling probably isn't related to your blood sugar at all.
Of course steer clear of excessive sugar and carbs until you know what's going on but honestly I wouldn't panic, dizzyness and thirst are both pretty common pregnancy symptoms and while they can be a sign of something, more often they're nothing to worry about.
Take care.