Is it normal to be in a relationship and still cruise dating sites?

Okay.. so in the first year of the relationship I discovered on my computer that my man frequently visited dating/fucking websites.. like adult friend finder sexsearch.com horneymatches.com etc. Along side he also daily would check out the escort section in Craigslist... one day I found out that he had a profile saying looking to fuck! He never hooked up w anyone but it hurt badly..he closed the accounts supposedly however he still surfs the Craigslist whores... should I be worried about his addiction?