I Am Nearly Two Weeks Late For My Period. I

I am nearly two weeks late for my period. I am always regular, having my period the same date every month (30/31 day cycle). My last period was 14th February. When it was due, I had all the signs that would usually point to the time of the month, then, nothing? I've had alot of stomach cramps, I feel tired and also craving sweets.. But I did do a home pregnancy test 2 days ago, but it came back negative. There's nothing different with my lifestyle/stress, I just can't understand why I am so late? This has happened twice before. They are my two children lol. But my husband had a vasectomy 3 years ago and the zero sperm count back then. Can I possibly be pregnant?! Thank.you xx