It could be the way you are approaching him for information. Men get very defensive if they feel they are being attacked or threatened. (example would be pointing fingers saying 'you did' this or that).

It could also be as simple as maybe he feels stressed about the wedding. Maybe he's nervous, or feeling uncomfortable paying for a wedding on a lower income as you stated. Maybe he just wants to talk about something else and not worry about the wedding for awhile.

I'm not him by any means, but given the situation it could very easily be any of the responses you've gotten here.