Hi. I Started My Monthly Cycle A Few Days Ago

Hi. I started my monthly cycle a few days ago but it was very light sometimes brown in color and skipped a day where it wasn't there at all. I also had unprotected sex twice with my significant other during a day that it skipped and now it is gone and I haven't had it.
It was never like this before and lasted four days but only two and a half if you count actual bleeding. My significant other did have unprotected sex earlier this month but when I took two home pregnancy tests they came back negative. Is this something I should wait to see if it is like this again next month?
What are my options and possibilities it could mean its never been this abnormal.