WTF? Negative?!

So, I went to the clinic to get my pregnancy confirmed this morning. It came back negative! I let the nurse know that I had a positive digital literally two hours earlier, so they went ahead and drew my blood. Unfortunately, I have to wait until Monday to hear back. I immediately went home and took three years - one Cheapie, one FR by dipping, and one by midstream. All positive - what the hell? Any opinions? Someone mentioned a chemical pregnancy, but the lines have gotten progressively dark since I first tested Sunday.