Hi,I've Been Using Nuristerate Since 2014 Always After 8 Weeks

Hi,I've been using nuristerate since 2014 always after 8 weeks I make sure that I cee my doctor on, the 28Dec 2015 it was my date I had to go,yes I did.on the 30Dec yesterday I had an unprotected sex with my bf.How long should I stay before unprotected sex.will it be possible that I can be pregnant since I injected not so long and had unprotected sex.