First Let Me Begin By Saying, I Have Made A

First let me begin by saying, I have made a few stupid decisions lately, reckless.
My question is, My last menstruation was Sept 16th. I am 45 years old and have been under enormous stress lately as I have been separated from my husband. Here is the bad decision part..... I have engaged in sexual intercourse multiple times from 10-03 to 11-1 and each time using protection of vaginal spermicidal film and or the sponge. I have not started my period, and have taken 5 home pregnancy test which have all been negative. So I feel I am not pregnant. But if I can complicate things even further....I also had sex with my partner 11-7 and 11-8 with no protection. I took another pregnancy test today because I still have had no period since 9-16, and the test today was negative. My question is are these test accurate? Do I need a blood test? How long from the 11-7 date of sex do I need to wait for certainty to know if I am pregnant or not? I have birth control pills to start but keep waiting for my cycle to begin so I can take them.