Why would he do this?

Ok my boyfriend says he don't care about me no more I don't know if he is playing are what.but his cousin was saying he is cheating on me so I asked him to see if it was true are not so he was playin like he didn't no what I was talkin bout he was like huh and he said who told u dat I said your cousin he was like hmmmm I didn't know how to tell u now I'm begining to think this whole thing was a joke to him I don't get this