16 dpo faint positive brown spotting

I have been TTC for 5 months, this month i thought I was for sure out because I ovulated on January 7th, and my husband left out of country on January 5th. We BD on January 4th. I am now 16 Dpo and AF didn't show so i tested 3 days ago and received a very faint positive, tested several more times and all faint positives. I have had brown stringy blood and enough spotting that i have to wear a liner. There has been a little bit of pink/red blood a few times I've wiped but no red flow. Is this common to happen in early pregnancy? Also is it possible for me to even be pregnant even though we BD 3 days before I ovulated? Or could this be the beginning of AF... I'm confused by the faint positives and the second line is not getting any darker. I did schedule a blood test for Monday January 29th to be sure. No other signs of pregnancy besides back pain which i blame on shoveling snow...