No period, negative test.

Hi y'all. Just had a question. My period is due today and I took a first response and a dollar tree test and both have come out negative. Is there still a possibility I could be pregnant? I noticed sore nipples a couple weeks ago and still have them but that is about the only symptom I have. With my first I had sore nipples and I was tired but I don't feel tired at all. Thoughts?