I would be asking for the money back ASAP.
My other half bought a house a few months before we became 'serious' or serious enough to be even thinking about moving in together.
He was in the army at the time and I lived on my own in rented accommodation.
It wasn't initially an issue as he was planning on renting it straight out and not living in it. However I became pregnant about 6 months later before we had finished renovations (I say 'we' as he was away 85% of the time so I oversaw everything and chose most of the fixtures and fittings).
We ended up moving into the house together. We're still here now, but honestly it is one of the biggest regrets of my life. We haven't had many, but when we've had serious arguments he always says 'you can move out if you're not happy', and it's very much at the forefront of my mind that none of it is 'mine'. Now I haven't contributed to the mortgage, or much of the bills either, if I'm honest. I refused to pay a penny to the mortgage unless we had a contract drawn to that states I was going to be included on it or entitled to something should anything happen. I mean the financial arrangement works for us, but still I absolutely hate the fact that it's not officially mine.
So please don't move into the house with him. If he's done this behind your back already, this would be serious red flags for me.
You're not being unreasonable in the slightest xxx