Period or implantation

I've had just a weird feeling that I may be pregnant. I've had odd reflux symptoms and extremely tender breast. I took FRER test yesterday (3 days before my expected period) it was negative.  today I have small pink spotting and light tugging feeling in lower abdomen.  Can implantation occur this late (2 days before expected period)? I did not test for ovulation but had unprotected sex during my possible ovulation days.i was pretty bummed when it was negative and I'm afraid I'm getting my hopes up again.  Thanks for your help!