Help!! No period negative tests

I’m really late for my period like 20 days late. My last period was October 7-9. My periods only ever 3 days long but my fiancé has been finishing inside of me multiple times after I had that period. I’ve tested a whole bunch of times and it turns out negative. I’ve read online in some rare cases you can’t have a positive till 8-10 weeks along. I’ve also had really really light bleeding for 1-2 days after ovulation in October and on November 11th he finished inside of me and today November 21st 3 days before ovulation I’m having very light blood and cramping. Can someone please help. Or try to explain this to me. Be nice thank you in advance!