So I Had Sex With My Boyfriend The Day My

So I had sex with my boyfriend the day my period ended. My periods last atleast 4 days or shorter since I am on birth control. But before I started my period, I was off birth control for about 4 days because I ran out and was out of town. He came inside of me, but right after I ran to the restroom and pushed it out. A lot of semen came out. What are my chances of becoming pregnant? Should I take a morning after pill in case?