Am I crazy or is he a good liar?

My fiance (age 25) (who I am marrying in 6 months) and I have been together for 8 years. We have never had ANY trust issues except I'm deathly afraid of being cheated on. I've always been this way. Well recently he texts a woman he works with (age 44) alot but only during work hours. I've read some of the text and they seem innocent. He has introduced me to her, we've met and talked. Nothing with his behavor has changed. He doesn't hide his cell or wallet. There have been no weird charges to his credit card, bank activity, etc. He doesn't cancel our plans, he is always home. I just am concerned that there is something there that I am missing. Would you be? I have confronted him and he has completely DENIED anything. Also, everyone at his job knows me, we have alot of mutual friends.