Bc and finishing inside

I’ve had my Nexplanon for a full month now and just finished my first 10 day period. I have a little spotting but it doesn’t bother. Starting last week, my boyfriend and I have gotten into the habit of him finishing inside of me. Sometimes it’s once a day and sometimes is three-four times in a day.

I’m sure my chances of pregnancy are slim but is it a possibility? Has anyone never pulled out on this form of bc?