Late period

Natalie👑 • Well, I'm Natalie. That's all
My period is late by 10 days it has never been this late before (last time it was three days) I've never had sex before but I have broke my hymen (stretching in yoga) Then finals were coming up and I had been studying my A** off for the time being. After finals were announced I had a bunch of final projects that were due on the 25th (my birthday) afterward my mom started to fear that I was pregnant and left a box on my bed I opened/ unwrapped it and it was Clear Blue Pregnancy tests. All four turned out to be negative. So what could it be? 
Is there any other way I can make my period exist in the pads I've been using?