Car wont start all the time

I have a 1992 Lumina Z34. Sometimes it will start right up and others it won't. The car will start up and kill right away on days it doesnt wana start. I have put in more oil because I know it likes to eat it but I put an adative in it thats suppose to seal up ring leaks and I also put in a fuel adative that will clean injectors and other parts hopefully this will help but if there is any Ideas on what it could be please help. I have been told several things like a fuel filter all the way to an ecm going please help. I also have a way of testing it by pushing my headlight button on and if its in the on position and the lights dont turn on the car wont start but if the lights do turn on the car will start so is it possible there is a connection between the car not starting and the headlights not working at the same time?

I also have a way of testing it by pushing my headlight button on and if its in the on position and the lights dont turn on the car wont start but if the lights do turn on the car will start so is it possible there is a connection between the car not starting and the headlights not working at the same time?

Sounds like you have some kind of battery or wiring issue. Check the battery cables and grounds. You might also want to get the batery/alternator/starter tested. some autoparts stores can do this.

Check for good contact & continuity through the main wiring terminal at the firewall. This sounds like a loose wire problem.

This morning my car died and before dieing more than usuall smoke was coming out of the exaust and then it wouldn't start Back up I believe my water pump might have went out long before I realized it. Could this be a head gasket if not what?

Whhat color smoke black, blue or white?