TTC. 4 days late.

Hello ladies!

My husband and I have been TTC since July of last year. I was supposed to get my period 4 days ago and it hasn't showed up. Usually when my period is late by a day or two, I start having some light spotting, but I haven't noticed any at all. I took a pregnancy test today, but it was negative. Just yesterday afternoon I started experiencing light cramping on and off and today also, but still no period. Should I test again in a few days? Has this happened to anyone else?