Here's my two pennies:
When you buy a round, get yourself a tonic with no gin ( but make sure that they don't give you a different glass - sometimes they do). Then next round say that they accidentally gave you a double and you'll just have a tonic water to top it up.
If you normally drink wine say that gin and slim line has fewer calories and you're mixing it up a bit.
Get yourself a clutch handbag and hold the glass in the same hand so you can't physically get it into your mouth! That helped me to remember. Then pop to the loo and pour some away.
Don't do a glass swap with DH unless you are SURE no one's looking.
At lunchtime you can use the driving later.
Keep circulating the room so people can't count.
There's a drink called lemon and lime bitters - lemoonade, lime and angostura bitters which looks like a long drink but isn't.
Watch the food. If people don't know you that well, it's easier to say you don't like pate/ cheese.
Btw - there's also a drug for thrush which is no drinking - that will shut them up.
I decided that I would go nuts at someone who asked me outright and tell them it is absolutely not their place to say such things then neither confirm or deny.
Fwiw, most people won't notice, particularly when they've had a few ( oh yes, turn up late, leave early). I was at a dinner with my MD and clients and I was the only one with wine left and still no one noticed).
Good luck.