Okay ladies

Help me out here? My boyfriend came over yesterday and I we were watching a movie. Simple enough

Things start getting a lil spicy but my parents were home so it was really just he had his hand in my pants and I was rubbing his boner.

So about twenty minutes pass and we’re just kinda touching and I let out a sound or two but nothing too hot. I unbuttoned and unzipped his pants and was touching through his boxers

Then his dick just. Goes away? Like 10 seconds go by and he’s soft. It kinda fizzled out after that and later it came back but WHAT HAPPENED.