By your description, it may be a MLC, in which case, you might be in for a long haul. I would say, be patient, continue to do the non-pursuit. This seems to get him thinking. I think the OW wants someone to look after her and her child. Perhaps the exBF wasn't doing so? Pointless, wondering about all this, though. I'm just wondering how he expects you to act, given that he has left you, and now living with OW and her child. I don't see why you should pursue him, or beg him to come back. You're better than that.
You're doing well, for one so soon in this sitch.
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim