Partner messages my ex

For some reason it seems like my partner has like an obsession I swear with messaging MY ex. It’s honestly annoying and I don’t get it, anyone else deal with this? He says he’s just being nosey but like leave the past in the past. It’s like this is his ex and past at this point.

Edit: I’m not completely sure what he messages him because he deleted the messages. He said he was asking questions he couldn’t ask me which I’m confused because I’m his wife. Then he basically said he asked if I ever cheated on him, asked if I had Twitter or OnlyFans. Then my ex messaged me that it was an emergency so I’m not sure what it really was because I couldn’t reply because my husband doesn’t want me messaging him or any other guys. It’s just all very weird to me but he says it’s normal and he’s making me seem like the bad guy for being upset about it..