Little bit concerned

Anon • Kaitykatt.xx
So me and my boyfriend were having sex about an hour ago. 
I'm on implanon, been on it for a few months. my period started on the 12/13th of this month in the middle of the night when I was asleep. 
We were having sex and the condom broke. He came fully inside me. 
What's the chances of getting pregnant?