Hi, I'm Married, 28 Years Old. My Periods Were Due

Hi, I'm married, 28 years old. My periods were due on 2 Jan , and it's delayed. I had slight spotting on 5 Jan and so I did a few pregnancy tests, all negative. I'm not experiencing any nausea however my breasts do feel heavy and I had cramps in the abdomen two days back.
(During sex, my husband used withdrawal as a method of contraception)
Could I still be pregnant?