Is boyfriend cheating?

We haven't had sex in over a month when we use to all the time. I bring him to work and pick him I can't send to see how he would have the time however wen I went threw his history I seen many dating sites what could be going on I spoke to him and he gets all mad at me and says he don't know how it got there please I don't understand he don't have sex with me anymore and it's cold towards me we barely even talk been together 12 years what do you think could be happening?
Is boyfriend cheating?
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