I'm sorry about your BFN. Are you doing the long protocol or the short protocol? If it's the long protocol, you have to skip a month to prepare, as you take the lupron a week or so after ovulation. So it wouldn't really be back to back. If it's the short protocol, would you start the meds on day 3 of this cycle?
Also, if you trust your dr and he feels it's ok, I would feel ok about it, too...
Good luck!