Maybe his response about his living arrangements was based on how he feels right now. It doesn't sound like you pinned him down on the real question in your mind which is 'if things worked out between us, would we get a place together and would you take an equal share of the responsibility and bills?'
I certainly would never have asked my DP this at 4 months.
The truth is, 2 years ago I was living with my parents (I own my own property but rented it out and moved in with parents to save money and go travelling). At 4 months I was staying at his 3-4 nights a week. I did do a lot of housework for him in those days, but mainly to impress him as I had such a strong desire to keep him happy. I'm not sure many men would do the same, and it sounds like your chap is being helpful in other ways. I personally hate mowing the lawn and taking the bins out so if he's doing that sort of thing then that would be enough for me.
For us to have a formal conversation that early on about 'will we be together forever' would have ruined the moment I think. Eventually we kind of naturally realised we didn't want to spend another night apart. I would suggest going home so he could get a good nights kip and he'd ask me not to and so I basically moved in and gradually more and more of my stuff ended up in his place. I initially paid my way by doing the all the food shopping, I then eventually started paying half the bills.
It kind of happened gradually and organically, we moved along as it felt right. But 4 months in, if he'd tried to pin me down to making a decision about the rest of my life or judged me for living with my parents things would have felt very different.
I think you should just see how it goes and enjoy the moment. Give it another 4 months and see how the land lies, a lot can change in that time. Believe me... I ditched the whole travelling idea, we bought a house together and now I'm pregnant!! If he's 'the one' it will be worth investing a few more months, if he isn't that's just life and you'll find someone else.