I just wanted to add my views as I am in the position of your boyfriend.
I don't live with my DP currently but eventually I will sell my current home and I will buy a home which is intended for our home together.
Luckily my DP also has a home but we've decided he keeps that in his name, I buy the house we will live together in my name and hopefully we can get a third property on BTL jointly.
I have always thought of the house I intend to be our home as exactly that. Whilst of course I want to protect my money/asset, I will want my DP to feel valued in the home so we will choose decorating etc together.
I think you should sit down with your DP and explain how his comments have made you feel. Explain that you fully understand that financially the house is his however if he wants to set up a home together then that should exactly be it.
You should be allowed to have an input into the décor an I would say perhaps you could buy the odd thing however big furniture should be paid by DP as ultimately if you were to split up, likelihood would be he would keep the furniture.
How have you come to the arrangement of how much you are paying? I've said to DP that I would cover the mortgage and I would expect the bills to be split between us. Initially I thought it should be 50/50 but actually I earn more money than he does so I would suggest maybe splitting 60/40.
Have you discussed things like wardrobe space and things like that? Will he allocate you half or expect you to have less room as it's not your house?
if I were you, the money you are saving I would put aside for the future just in case anything crops up and you have to move out.