Std's

Has anyone ever had a false positive for an HIV rapid test? The one that takes 10-15 minutes with drawn blood.  I recently had some testing done, as I always do every six months just to be safe. And they called me back saying I had a verrrry faint, not even sure if it was positive line on my test. But still had to mark positive and send off a confirmation test to be 100% and would have results in a week. I'm stressing Tf out, although I'm sure I'm not infected I've been with the same person for 4 years. And was just previously tested in October for my pregnancy. So again, my question is has anyone had false positives on this rapid test and have the second one come back negative? Is it common?