Feeling concerned in need of advice

Okay so i consider Myself Irregular, although i been regular for four months already(something new for me) foyr months back i started getting my per. Every 13th on the clock every month. This 13th of october i was waiting for it and i did. Get it everything was normal spotting amd day #2 more spotting but day #3 nothing!? I never really stained my pad. Okay im worried because Oct. 5th i had unprotected sex, and even tho i do want to Be pregnant i dont want to get my hopes up. Okay i did 3 pregnancy tests at home all neg. So i left it but today Nov. 4th i got more spotting so i dont know what could be going on?