Hi, if your period was due and spotting started on Thursday, chances are it is NOT implantation bleeding, which should've happened earlier on, right around your fertile days. Or, in other words, any implantation bleeding would've happened around the middle of the cycle.
This sounds more like an early period. Having said that, once unprotected sex is involved at any time, we cannot rule out a pregnancy. A home pregnancy test performed after you miss your period will tell you for certain. all the best!
yes, waiting a few more days and repeating the preg test is recommended. however, sore breasts, nausea, headches etc. are general conditions that may or may not be pregnancy symtpoms.We can never go by them to conclude it's a pregnancy.