Spotting, negative test, no period

Hi everyone. My husband and I tried to conceive for the first time this month. I am very regular with a 32 day cycle. About 10 days after O I started spotting brown for 5 days. Very little blood, a couple drops in toilet and on toilet paper. I took a first response test the first day of spotting (about ten days after 0) and it was negative. Three days later I took another one. Still negative. Now, my period is 3 days (and counting) late which is very unusual for me. Anyone have a similar situation? I'm thinking I should test again but don't want to see another negative. I have an appt with my Ob oct 16.