AreWeThereYet
Instead of judging him based on the reasoning of a number of unknown people why don't you ask him why he did it?
Maybe he feels you are out of pocket and is uncomfortable with it. Maybe he misinterpreted something you said at some point. You could always just tell him you were perfectly okay with the previous arrangement. Maybe he wasn't for some reason.
His answer could tell you exactly what you need to know.
I am with this too, I think it is strange you do not feel comfortable enough with him to just laugh it off and say what is all this about. I would suggest you in future PAYG, which I always did with my partner of 10 years. we did not live together and had totally different income, so I never wanted to feel I took advantage of him being more comfortable than I am. My partner was also tight, in fact I almost finished with hime during the first couple of years, because he expected to eat here daily with very little or no contribution, but we sorted all that over time, as we got more and more fond of each other.
It is much more about whether you enjoy being with him, find him fun, interesting and generally good company, It is essential you are able to discuss anything and everything with him and feel comfortable about it all in my view.