What Causes A Missed Period Here?

I missed 4 days of my birth control pills from 9/29-10/2 and I got my period during these days, really heavy. I took all the ones I missed plus the one for sunday all on 10/3 and continued taking the pills as if I hadn't missed any days. I had sex, while I was back on the pill with my continued birth control cycle and he wore a condom, on 10/10 and was supposed to start my period on 10/12 and have not gotten it yet. Could the missed period be because I had it when I forgot to take my birth control or is it because I'm probably pregnant. Also, I took 5 home pregnancy tests and they've all come back negative. Are those going to be pretty accurate or is it to early to take a pregnancy test?