I want my bf to cum inside me every time w/o getting pregnant

What do I do ? :/ 
I am on depo shot  got my next shot in april.. I just recently got sexually active.. 
Do u girls take a risk or is depo shot trustable. We used to use condoms and then started doing it without as it felt better. He came inside me for the 1st time idky but I liked it and wud prefer him to cum inside BUT I DONT WANT TO GER PREGNANT :(