I think it's clear why he wants to move in more than you do. This benefits him far more than it does you.
I'm not saying that there can't be benefits to living together if you both really want it and are clear about expectations etc i.e., household stuff, bills, etc. There can be, but if you don't really want this and are feeling pressure from him to take that step-you could end up feeling quite resentful should you decide to cave in.
If you are going to do it, you need to protect yourself and your assets. It's all well and good walking into this with rose-tinted glasses on, thinking he's not the type to make a claim on something you've worked for and built-but if you break up and there's bad feeling-would that still stand?
Get in touch with a solicitor and draw up a cohabitation agreement, clearly outlining that he has zero stake in your property. Do not put him on the mortgage deeds. Don't allow him to pay towards the mortgage. Don't allow him to foot the bill for any major renovations to the home that could increase its value.
Be very clear that he holds the status of a lodger and draw up an agreement, stating such.
Honestly-his reaction to being told that he won't be having a stake in your assets will tell you all you need to know about his intentions.
In the end, you have to think about what you want, not what he wants. If you're not comfortable or eager to move in, that's your answer. Don't feel pressured to do so.
I have a boyfriend of four years, and we live separately. I have my own place and I don't want to move in together at all. Part of that is to protect my asset but also to protect my peace and my space. I know society says it's the "next step" and the "done thing" but why?
Do what works for you and if it no longer works for him-then it may be that you're not compatible.