Hello,
Recently I've noticed my DP tells little lies about strange things.
One example:
He is a driver, had an issue with his car and needed the spare set of keys, someone dropped them off to him, there was another issue and he asked me to pick him up from where he left his work car. We were chatting when I picked him up and he said a 'he' dropped the keys of to him, then later on in conversation said something along the lines of 'Kate was on the way back from office so dropped them off to me', then looked at me with a fearful expression.
Now I'm not the jealous, insecure type so I wasn't bothered that Kate dropped them off to him, I just carried on talking.
I found it strange that he lied saying it was a male who dropped them off. He said it was a male several times before saying it was Kate, so it wasn't an accident.
Other times he says something and when I mention it as I don't agree with it or want to challenge something, he says oh I can't remember saying that.
I'm not argumentative but I do challenge him for example I'd say, why did you say so and so? He usually explains and that's the end of it, but recently, he just 'doesn't remember' even if it was 5 minutes ago.
We're both 30 so it's not his memory giving up 
He lies about the most insignificant things that I would not care about, but the fact he lies drives me insane.
I thought about calmly mentioning it to him tonight, or wwyd?