Help!!! Weight loss & dress fitting

Hi all,

I have been losing weight rapidly and I have lost 22lbs since May 30. I tried on a wedding dress last month and I was a size 24. I tried on the dress again last week and I went down to a size 18 so I ordered the dress last Saturday expecting it to arrive in October but it arrived today!! The dress fits as it is now but I am losing so much weight I’m scared it won’t fit by my wedding and will be too big. I am averaging 3-4lbs weight loss a week. I would like to order a size 16 because I only would have to lose 2-4 inches to fit in the dress. I have no intentions on stopping losing weight and I don’t want to maintain until closer to the wedding. I also don’t want to pay a lot of money in alterations but I know they can bring it down to a size 14 altering it. The dress shop is giving me 2 weeks to make up my mind and the dress is final sale so no returns. My wedding is on Nov 10. What should I do? Should I order 1 size down? I’ll try to attach a photo.

Please help I’m about to cry!