If i got the nexplanon implant on the 5th day of my period and had unprotected sex in the next day or two will i get pregnant? or will the birth control stop the pregnancy from developing if i am?

"Nexplanon" implants release progestins, which act as contraception, and if ovulation had not occurred early ( on "day six or seven" of your menstruation) , the Nexplanon method should protect to the limit of its capacity, which is not "100% certainty". If your next cycle is delayed, obtain a serum HCG test to be certain, but once pregnant, Nexplanon will not affect development.