I am sorry for your m/c ;o( lets hope this is not the case....BETA is the blood test to ck on pregnancy levels, not the one that says YES or NO, is the one with numbers which doctors use to see how many weeks pregnant you are.
I really hope you aren't having another m/c and this is just one of those crazy things that sometimes happens for no reason.....maybe give your doc a call.
I am still taking Yaz and I am not familiar with the Beta test? I have already had three miscarriages and don't want to have another one.
brown spotting means old blood, sometimes pregnancy tests can take a little longer to show +....have you done a BETA test? are you still taking YAZ?