Pregnant on Nexplanon??

I got my Nexplanon placed on May 27th. Two days later, I started my period. I haven't had a period since May 29th and keep getting faint positives on pregnancy tests, along with plenty of symptoms. My fiancée and I had sex June 15th and I'm pretty sure I was fertile that week. Other than Nexplanon, we didn't use any protection. My question is could it have taken longer than usual for the Nexplanon to kick in and I'm actually pregnant?