We had what we thought was a faulty toilet it flooded our downstairs living room. Replaced toilet and subfloor and everything. All good for about a month. Heard NEW toilet constantly running, Found water coming from ceiling again!! What could it be? Is there a pipe or something that tell the toilet to not get anymore water? I thought maybe I need to call a plumber with a pipe camera..? Any suggestions would help!!

You have two problems here.
1) The running toilet. Tell me what's running. Is it leaking from the flapper into the bowl? Won't the ballcock shut off? Please explain with details.
2)
we had what we thought was a faulty toilet it flooded our downstairs living room.
Thar's where you made your first mistake. Toilets just don't go "bad" unless you drop something and break the bowl. Something on down the line caused the toilet to back up.
The first thing I would do is pull the toilet and snake the branch. Then I would reset the toilet using a new wax seal. Let me know what you find when you run a snake through the toilet drain. Good luck, Tom