CRA benefits - asking for address proof which I don't have

So I have had no income in some years now and didn't file taxes for those years until this year where I filed this year and the previous years - in order to get the credits that I am supposed to get retroactively for the previous years.

CRA decided to ask me where I lived all of those years I only had one address on the forms cause its the one I lived in the most and could get mail at. Since I had no income I lived with people (I only provided one address to them which was the one I could get my mail consistently at - where I lived with my ex)

The person that did have stuff on their name was my ex - which I do not want to contact for any letter from and not sure if he'd be willing to do that anyway (and its not what they asked in their letter anyway - they asked for rental agreement, utility etc in my name - 3 for each year - which I do not have - but maybe if I say I dont have they would ask for me to give a letter/affidavit from the person that I was living with which I don't want/can't do as explained).

So what do I do? I have a feeling if I just mail back saying that I don't have (and if they ask for a letter/affidavit from the person I was living with and I say no with no explanation or say that it was my ex and what I just said - they will just deny the credits. so I just filed it all for nothing and won't get anything out of it anyway)

Why do they even need proof of my address? the credits are federal and apply to all provinces. regardless of address (what about homeless people?)

If you have any advice or anything to let me know what to do in order to get the credits without those documents, please do. Or if you have had similar thing happen.