Your problem is not with the camshaft. Please refrain from getting any engine head work being done, your problem is totally pointing in the other direction.
Get your Fuel Injectors checked, there's a bright chance they might be clogged.
Your Fuel Filter will need replacement as well.
Your Fuel Injector Rail will need to be replaced too.
This happens when you drive on CNG while there's little Petrol in the car tank. When you switch to Petrol, the deposits in the tank then clog the fuel lines and eventually the injectors.
You will get a set of Kabli injectors from Shershah for around 4k, try finding good ones and get them checked before buying, this is very important !
Get a brand new fuel filter when you get this done
Better get this done as soon as possible because your car starts on Petrol and THEN converts to CNG, if the condition of the injectors gets worse, you'll have more problems.
If you can afford brand new injectors, that would be the best solution since Kabli injectors are just temporary and won't last you as long.
Hopefully this will help you, keep us updated