My period is late. Answers? :)

I got my period the 29th of October till November 3rd. On my other tracking app it says I am 2 days late and this app I was suppose to start my period yesterday. I'm not saying I am pregnant but I do have unprotected sex using the withdrawal method. My last period was shorter than normal. Is it any chances I am pregnant? And I haven't really thought about being pregnant,I'm just wondering why my period is late because I am regular.