finishing the job

So, my better half and I don't use protection. And he's never had an issue with this, but here lately he has been saying he got off, and I can tell different in the nasty mess of my goods. Since we are trying for a baby I asked if he actually got off he said yes. But when I walked into the kitchen. I fought a glimse of him in the bathroom wiping off his penis and saw shots on the floor. He knows how serious I am about trying but he either pulls out fast or asks to go in my mouth. With that being said I can also tell he hasn't finished being that there's no warning, he just quits and says he got off. Why would he be lying. Does he think I'm stupid?