Late and cramping. BFP?

Hello! AF was supposed to show last friday (11/7). The day before I did a blood test because I had sinusitis and the doctor thought it was best to check since I'm TTC. The teste came negative. I took another one (pharmacy) last tuesday because I still had no signs of AF and was on meds and got another BFN. Now I've been cramping since wednesday and still no sign of AF. A BFP is still possible?