Needing advice!

I had unprotected sex with my boyfriend last month during the time I think I was ovulating, I was thinking I was pregnant so I took a clear blue digital 4 days before my expected period. Negative. So I waited for my period to come. Well it came one day early which is normal for me but it was super light. Usually when I start, I'm heavy from start to nearly finished. But my period was very light for 1 day then a tad bit heavier for one then light again, then stopped. Usually my periods last 7-8 days. Not three. Now I'm feeling nausea when I wake up, after meals, randomly through the day. I had a couple weird cramps and very emotional. Not supposed to start my next period for like 20 days but could it be possible that I am pregnant and I had weird implantation bleeding?