Whhhhhy

I'm almost 3 weeks late. Last hpt taken 3/5 and still got a BFN. I have slight cramping today, I'm constipated and my nipples are really sensitive. Also producing a lot of watery CM.. I'm just waiting for AF to show her ugly face any second now, but I'm going crazy. I want to keep testing, but I don't think I can handle another negative. We have been TTC since September 2012.