MY BF CAME IN ME AND WONT ADMIT TO IT 😤

So I'm on birth control and we have sex without a condom but agreed on pulling out each time just in case. Well there have been a few instances in the past where I thought he came in me and he denied it. It's hard for me to feel if he has or not because he doesn't shoot out cum, it just kind of plops out, and I get crazy wet and when I orgasm I cum a lot so it's hard to tell the difference.
But those times he just claimed he just couldn't cum. 😑
But tonight I know for a damn FACT he came in me and he denied it and said it was just precum. 
He said "why would I lie to you?" 
I said "Idk because we never agreed on you coming in me?"
He said "yeah but you wouldn't care because you're on birth control." 
I'm like "Did I ever say I wouldn't care? No!"
And he said "Well I didn't cum in you, you're trippin. I came in you maybe once or twice in the past but I told you."
And I'm like "NO you never told me!!" 
He keeps denying everything. 
Please help me how to have a calm discussion with him so he will open up to me and be honest with me!! I just want honesty.