What does this mean?22F M29

What does this mean?

{I’m a 22F} My boyfriend of 3 years (29M) tells me this every so often; it’s “you’ve been hanging out with other boyfriend” your other boyfriend….” This and that tbh. He doesn’t accuse me of having another boyfriend directly but he puts it into those phrases I listed above. When I tell him no I don’t have another boyfriend he doesn’t even acknowledge it and brushes it off; it’s been going on like this for a while and no I have never cheated on him before. So basically why you or another man do this.