Nexplanon,Period, Sex

So I have 2 questions..

1. I got on Nexplanon like 9 days ago... am I protected from unprotected sex with my bf? Like has it taken effect?

2. I started my period Sunday it was like super super light (I usually have a heavy flow for 4 days and 3 days light/brown) and then it stopped. Started the next day, stopped, and now these past couple days have been getting heavier and heavier.. is this just a symptom or is this how my periods are gonna be now? Also my cramps are more occurring this period