Caught him lie

Found out my bf was looking at innapropriate pics of girls... I wouldnt be so upset, but he always brags about how he never looks at that stuff and has promised I'm the only girl he looks at. A lie is a lie. It would be one thing if he never said that or made any promises. I don't think this is my fault.

How do i confront him about it? He is always quick to point out my shortcomings, so i feel like he has this coming. Keep in mind, we are two years in and live together.