Possibly preggers?!?

Ok, so my husband and I haven’t been trying but we haven’t not been trying (if that makes sense). I’m not on birth control, and haven’t been for the past 4 years, but I’m not tracking my ovulation days or anything.

So... I’m 16 days late for my period...I’m usually pretty normal with my periods coming between every 28-32 days and lasting about 4-5 days... I have been having light spotting in a dark brown color for the past 3-4 days with mild cramps... but I have taken about 4 pregnancy test over the past 2 weeks and all of them have said negative! The one I took on Friday said negative as well... however, that same day is when I started spotting this dark brown color.

Could I be pregnant? Or am I just over reacting? Has this ever happened to anyone before? And what was the verdict?