Hiya, I want to be 10 stone in 117 days for my wedding. I think one month for your goal is a lot of pressure! (I have 22lbs to go).
So far I have been dropping an average of 7lbs a month. So 18lbs seems an awful lot to me! Your current 3lbs a week is excellent and a healthy range, don't put too much pressure on yourself! you are doing brilliantly as you are.
You need to have a deficit of 3500 calories per pound lost. So basically you would need to be cutting out/burning off 14,000 calories per week to loose 4lbs and that is A LOT!
Good luck to you, sounds like you're doing great. Just be sensible and healthy about it or it might go straight back on when you return to normal. Have a lovely mini holiday! x