Would add, any bills or purchases in one or both of your names - as long as not just from one of you. Any correspondence or bills, deliveries, payments for furniture purchased, etc.
You can also get letters from friends/family or lease agreement from parents.
Note: since you have been together for several years, document that as well. if that long-term relationship is well documented, the question of how much proof needed of living together after being married will likely be much less important.
[Or to put this simply: a couple that has only known each other for a month before legal marriage obviously will need more proof of living together after marriage to be credible. A couple that documents well their five-year + relationship living together and has kids probably doesn't need much at all. (Those in between, like you, well, in between those two cases)]
Warning (for others reading this): proof of living together for common law spouses is a different matter with its own nuances and critical points - eg a couple can be married without ever having lived together, but not common law.