What Causes Pregnancy Symptoms While HPT Is Negative?

Hi, I ve just recently started getting pregnancy syptoms ( sore and tingly nipples and sore breast, nausea, cramping, tiredness, dizziness). I was previously on the depo shot for 2 years until early in December. I had a short period of about 2-3 days and then got with my partner early in January, we had unprotected sex nearly every night. Ithe last time we slept together was the 19th of feb. It s was about them that I started noticing the pregnancy syptoms. I took a blood test but it came back negative. Is there anyway this could be wrong? Could I be pregnant?