I agree with timelylass's post, but that being the status quo, what do you do next? You do have the power to make some decisions.
I was in your shoes once and I had to decide that I couldn't sink another minute in to feathering his nest. It was difficult but I left. (Now I'm so, so glad, but that doesn't take away from how hard it was at the time).
If you believe the relationship is good, then it's worth being honest about what YOU want. It's ok to have an agenda. It's perfectly acceptable for you to have a life plan. What you wanted was x, y or z. Say it out loud. Remind yourself that he has structured this family unit in a way that has suited him. Ie, how he wants, together but not married. Why therefore is it not ok for you to be upfront about what you want.
Put it to him one more time; bluntly. This is what I want. Be unapologetic about it.
Either he will acknowledge that what you're asking for isn't at all unreasonable and he will take legal steps to protect you financially or he will want to get married to you too.
If he wants to continue with the relationship as it is, ie, a situation that suits him, costs him nothing in terms of risk, or sharing or compromising, then be strong. You can no longer afford to invest your time and your energy and your labour in to the relationship.
I left and after 8 years of feathering somebody else's nest, paying their council tax, paying for groceries etc.... it took me a long time to recover financially, but luckily due to a change in circumstances I in a much better situation now and I do not regret leaving him for a second.