2007 NIssan Sentra SE-R 2.5l causing problems

p0420 and p0430 codes, and engine oil burn

So, I just bought this car a few months back and everything back then was great no check engine light or anything like that. But few months passed and engine light kept coming on saying catalytic converter below threshold (p0420 & p0430) and now its permanently there and will not go away and on top of that, this engine is burning a lot of oil. Any time I check the dipstick it never shows a drop of oil unless it just had a fresh oil change. I watched you video and tried cleaning the PCV valve first and that made no difference at all, I tried using various cat cleaners to see if they would clean the cat but none of them worked at all. Are there certain steps I should take in order to figure out the problem or to even fix it? Please let me know and your help is greatly appreciated.

oil burning engines ruin cats, so odds are yours is ruined. Replacing it, will just ruin the new one. Rebuild the engine and replace the cat, or get rid of the car

By rebuilding the engine do you mean replace the valve cover and gasket or like a complete rebuild where i have to take out pistons and replace the o rings and such. Lemme know also thank you for your help.