In my opinion only (and I could be wrong): the living together first during your app / then living together when you got your COPR is not going to look good.We lived as roommates for 2 years. The day I applied for PR we lived at different places and stayed apart for 9 months. Then again shared address for 6 months. During these 6 months, I signed my ecopr. Then again stayed at different address for next 10 months till we got married.
The fact that your (romantic) relationship didn't have a clear document-able 'start date' doesn't help.
Was this an arranged marriage?