When am I least likely to get pregnant?

Hello!
I am 26 years old and on the pill. However, even though I'm good about taking it around the same time each day, I am really nervous about getting pregnant so I don't like to have my boyfriend cum inside me even though I'm on birth control. Basically, we use the pill method along with the pull-out method.
My issue is that I love the way it feels when he cums inside me, and I know that he loves it too. I would like to let him cum inside me from time to time, and am curious when I will be the LEAST fertile so that it won't freak me out to let him.
Any help or guidance would be appreciated!
Thanks :)