pregnant?

so I had my period starting on August 4th and it lasted 11 days and I finished the 18th. My boyfriend and I had sex while I was on my period and my fertile days using no protection. As of yesterday (August 19) I started spotting in the morning and then there was nothing for the rest of the day then today I spotted in the morning but there hasn't been anything since. The app says my period is still 8 days away so I'm just really confused. What could be causing this?? Please help!!