I Have T1DM, Treated With An Insulin Pump, Novolog Insulin;

I have T1DM, treated with an insulin pump, novolog insulin; I also have PCOS that's treated with metformin XR 100mg BID. Since my diagnosis of PCOS and starting metformin in 2011, I have never skipped a cycle or went longer than 32 days. Usually I can predict when my cycle is going to start by my bg level (it's elevated 4 days prior to starting my cycle). Today will be day #41 and my bg levels have been wnl. I did a hpt last night and it was negative. My ER physician tonight said that it's possible that T1DM can sometimes cause a false negative, he had heard it somewhere along in his residency..but my research is falling short on providing sound literature on this topic. Is this possible? Before I make an appointment with my OBGYN and she laughs at me ( I work with her and she's a friend).