Irregular periods

My husband and I are trying to have a baby. I stopped pills the beginning of August. My period was on Aug 30th till Sept 5th. It was normal. Heavy 3 days then light. Then my period happened again on Sept 15th. It was 2 days heavy,2 days light. I did ovulation tests for 10 days and nothing. Didn't buy a new pack to keep going. It's Oct 5th and no period. Took a test..it was negative. But should I believe my period is late or is it going to start around the 15th? We had sex 4 days out of 7 during the supposedly ovulation days. According to the online calendar.