birth control effects (TMI and Picture warning)

I just got my Nexplanonon my arm about a week ago and I've been breaking out wayyyyyyy to much is this gonna keep happening for the next 3 years? If so any recommendations on how to control it?!?  And my friend also told me that if I have sex with my boyfriend and he cums inside I could get pregnant but the Nexplenon would cause me to have a miscarriage 😶 is this true?!