Keep in mind, everyone gets cold feet the last few weeks, so what you are feeling is normal nerves. BUT there are people that get the surgery and regret it long term, so use this time to weigh all your options.
Option 1. Get the surgery as planned.
2. If you are a candidate, go with a sleeve instead.. fewer complications (but if they do happen, they'll be just as expensive as the bypass ones).
3. Cancel the surgery, with the understanding that you may reschedule when you are comfortable.
4. Reschedule the surgery for January.
5. Have the surgery in Mexico, and that would leave quite a bit of money in your bank account to help with any complications. (I went to Mexico with Dr. Illan, and have no problem recommending that option to others. It was a very good experience.. and Dr. Illan is willing to help with any future issues, you just have to be able to fly down for the care).
Complications from surgery would be expensive, but so are complications from morbid obesity. Diet and exercise programs are a bargain, so if you haven't tried them, that may be a great thing to do if you choose options 3 or 4.