For me, yes, it was common to not have any signs and still get a bfp. I go not symptoms whatsoever until after AF was due, and even then I still didn't get m/s or sore boobs until after the 6 week mark (so 2 weeks after AF was due). Basically I just felt normal. If it wasn't for the positive tests and no period, I wouldn't have even thought I was pg. I also never got positive hpts until at least the day AF was due.