HI Meggan and welcome...
You understand WHY your Dr wants you nicotine free prior to surgery, right? It impedes healing. So you have slipped a few times. Please make those times your last. Second hand smoke Does get into ones system, that is a fact, so it makes sense to me it would effect a test. Unless you live with your parents, if I were you, I would avoid them until well after your surgery.
I had an emergency gastric bypass a month ago. I am healing nicely. I chalk it up partially to the fact I quit smoking over 3yrs ago.
Since you have to stop smoking anyway, please take this time to commit to stopping for good...I mean, if you are ready, that is...as smoking is very hard on the stomach, also.
Best of luck...