Can my blood test be wrong?

My last period started dec 3. I had unprotected dec 16&17. My nxt period was due jan 3rd. I've been having light cramps in my pelvic area, sore , and nauseous after I eat. I always feel like my periods coming but it didn't. I took a blood pregnancy test on jan 3rd. Could it be wrong? My period has always been regular. It always start the exact same date as the previous month. Why am I having pms symptoms with no flo?