Im 35 weeks pregnant and used meth and i have previously failed my first drug tests. i don't want to let my doctor down but what should i do wait or tell her and will i lose my baby?

If you are on a CPS watch list in many states they are required to test baby for drug exposure. If it occurred after 12 weeks I can find evidence of that exposure. You should always let the doc know your situation so proper care can be provided for you both. In my state you would automatically be scheduled for at least temporary loss of parental rights due to the earlier failed test.