It does not mean that he is cheating on you. Take it as sign to change few things.
May be , You are doing something which is pushing him away from you.
Sometimes too much philosophy or intellectual talk can result issues in relationships.
Are you always focusing on his flaws? Are you always picking up points where he is not doing well?
If that’s the case then there is serious problem.
Men try to stay away from all this by keeping themselves at work or hanging out with friends.
For a minute, look with in you & analyze your actions.