Can guys always tell when they’re about to

Cum? My boyfriend and I always use the pull out method and sometimes condoms. We also usually have fast sex but last night he was on top and he was going slower than usual.. all of a sudden he says “oops!” I’m like oops what? Then he said he accidentally finished inside of m because he wasn’t used to going that slow and didn’t know he was about to finish. I’m just wondering if he finished in me on purpose. Is it possible he really didn’t know ? Because I always know when I’m About to cum. But at the same time he’s 30 and was a Virgin up until 6 months before meeting me. Before me he’d only had sex twice but we’ve had sex a lot.. opinions ?