A week late...

So previously I put up a post stating that my period was late. When me and my boyfriend have sex it is always protected and he has never came from having sex either. I had recently went off the birth control pill back in August and my cycle was as regular as it could get up until now. I have had light pre period cramps the last week and a half and had other period symptoms as well. I took 2 pregnancy tests when I was 3 days late and both were negative with no second lines whatsoever. Any ideas of what could be the issue???