Can I still be pregnant

Asia

When should I seek medical advice? My last period was on August 4th-8th. Between August 14th-28th I used the restroom wiped and it was light pink on the tissue once that day. It's now September 30th and still no period. I have done about 8 urine pregnancy test different brands and no positive results. I have had unprotected sex a lot with my boyfriend. My periods are regular as well.