late period ... slight cramps

I should have gotten af nov 23, and still have not gotten it. I tested the 26 but was negative. I am nervous to test again cause I don't wanna see another negative. Since the 27 I've been having cramps like I'm on my period but still no af and I haven't had any symptoms like I usually do when it's supposed to come. Anyone have advice? I have been ttc for months now. I noticed when I was ovulating in early nov and made sure to have sex.