Hmmm yes I'm sure he was 'confused'. Sounding more and more like he's taken you for a ride OP. Explain to him the legal standing and protection marriage woul give you in the event that he died/split up from you and ask him how, in the absence of marriage, he proposed that you guarantee that protection. Examples you could suggest might be him writing a will that makes you his sole beneficiary (especially important if his family don't like you), putting your name on the deeds of the house, any savings you have as a couple being in an account in your sole name (on the gentleman's understanding you would od COURSE give him back what he put in in the event of a split.... You know, the kind of security he is offering you over the house).
When he weasels or flat out refuses these options, explain to him that what he is telling you is he doesn't want to marry you the better to screw you over when you split (which is obviously a when in his mind, not an if). And that that is not acceptable to you, not what he promised when you combined your finances and had his child, and a total mug's game. Does he think you're stupid?
Presumably you announced this engagement in some way. Ask him how he plans to explain to your friends and family who are presumably expecting an invite at some point that he has decided, at this late stage in the game, it is "too much faff" to fulfil the promise he made to the mother of his child to make a full legal commitment to her, but he would like to keep on fucking her for now so you're not breaking up? How is he planning to parse that to, say, his mother?
Honestly what a prick. At least he's being quiet blatant though instead of just stringing you along for decades, so just believe in the face he's showing you and don't waste any more years on this idiot. Start making plans to leave and make sure EVERYBODY knows why.