Don't know what to do

Amie
I am due my period today, it hasn't come yet. I did a pregnancy test two days ago and it was negative as expected. Reason being the last time I had sex was 2 days after my last period and believe it wasn't possible to get pregnant this early in your cycle. My average cycle is normal 31 days and Im very regulare the past 6 months (finally after having my lg 2 years ago) 
I have had a good cry this evening, hoping its hormones but I can't stop weeing! Which is concerning me abit. 
Do we think it's just a late period or is there a chance of pregnancy