Would you tell your ex ?

So im currently 6 months pregnant with my exs baby

He says he wants to be in the babies life. But yet doesn't respond to any texts about the baby or didn't care about going to the ultrasounds ...

Anyways. I recently started talking to a guy. And things are going okay. We aren't 'together' or anything. But he's around .

Should i tell my ex . Or let him find out on his own ?