Implantation or spotting before period?

Kaylee

I’m currently 4 days late on my period. I had sex on January 14th unprotected. My last period was dec 27th-jan 1st. But before this spotting I had acne, constipation, backache… I’ve taken 3 pregnancy test. Two on the first day I missed and both negative nothing faint. Took one a day later and negative as well. So I’m lost on what to think. Please help