If he's lying to you because he's noticing other women, it's because he believes you wouldn't be able to handle knowing that. In other words, your behavior/actions in the past has led him to conclude that if he were to say "wow, that woman is beautiful", you'd lose it and be angry with him or lapse into a pool of insecurity about yourself.
The thing is, just because the two of you are married doesn't mean his eyes and brain don't work anymore. He can SEE other beautiful women, and sometimes he's going to THINK about them. All guys do that, but for most guys, it never goes beyond that, and as long as he isn't disrespectful about it, it shouldn't bother you. It doesn't mean he's any less attracted to you, or that he loves you any less.
What it DOES mean is that you two have a communication problem. Neither of you are being fully honest with each other, and that often happens when one person can't HANDLE full honesty. Can you? If you can, then you need to tell him you can, and get back to a place where you can be completely honest with each other. Trust me: you'd be far MORE secure if you were being honest with each other all the time, even if you didn't always like or agree with what you heard from him.