HELP PLEASE

Last year in October my period started to last only 4 days but it went back the normal 6day cycle in December but on December the week i ovulated i had unprotected sex because me & my fiancé want kids so in January i had medium flow bleeding which was super dark burgundy but then turned pink & it lasted about 2-3 days? Then i started to spot & it was pink for about 3 days then now in February i was a week late & i had unprotected sex on February 1st I wasn’t supposed to be fertile since my period was supposed to come on the 6th but i had a heavyish flow on the 13th & it lasted 2 days now im just spotting again i took a pregnancy test on January 30th and it was negative so help please before i make doctors appointment:((