period is late negative results?!

So AF is no 6 days late which is very abnormal for me. It's always on time. About 3 weeks ago I had some light spotting that was pink in color for about 3 days off and on. I've also been getting random cramping in my stomach that only last for a few seconds. I'm not sure if that has anything to do with my missed period or not, but it does worry me. I have taken a pregnancy test, but it came up negative. I'm completely confused and I could really use some advice on what could be going on with my body. Thanks in advance ladies!