Could I be pregnant on the pill!!!!??

I have been taking birth control since I was 13. I had very irregular periods and have PCOS and Hypothyroidism. I haven't missed any days in my pill pack for a long time and take it around 9pm every night. I know it's normal to miss periods on the pill but I normally have some type of period every pack. On August 7th I had sex with my significant other and he came inside me. Two days later(August 9) I ended up having very bad pain in my lower abdominal. I took a test and it was negative (my nerves got the best of me) and I was also taking azo because I thought it was a uti because there was burning when I went to the restroom. My doctor then that Friday (August 11) gave me a prescription antibiotic to help clear up the uti. I wasn't feeling very well, but continued to take all medicine as prescribed, so pill and antibiotic. That Tuesday (August 15) it had been a little over a week since intercourse so I took another test and it also came back negative. This was a first response test the 6 days sooner test that the pharmacy said wouldn't interact with my current medication and antibiotic.I know some antibiotics can affect birth control, but I didn't start the antibiotic till days later. I started my placebo pill (period pill) Friday (August 18) I don't normally start my period till the second or third day and still really nervous I took another first response test Sunday (August 20) because I'm two days into my period pill with no period but I have discharge in my underwear. This test came back negative as well. The antibiotic I started taking August 11 was making me sick and wasn't clearing up my uti so my doctor order a different antibiotic which I started August 19 (this past Saturday) that so far has worked wonders. I was hoping to wake up today August 21 to a period and I have yet to start. I'm now 3 placebo pills into the week and I'm getting worried. I have had some fatigue and I'm still on an antibiotic for a uti that's clearing up. I time to time have some pain in my lower right side. I have eaten fairly normal. I have had some small back cramping like a period would do that started after taking the placebo, but nothing has happened. I've taken 3 tests all coming back negative and I feel as if I'm frustrated. I have talked to some friends about it and my significant other. Everyone is on that I'm not pregnant. If I miss this period on my pill should I take another test? Should I even be worried about pregnancy? I've just never had this happen and I'm anxious, scared, and just don't know what to think. Any advice would be great or if someone has been in this position and would share their outcome that would be even better. Any advice on helping my period come would be appreciated as well. Thank you!