Headgasket?

[grim reaper01]

Hi ya all I'm a newbie so hope i'm doing things right.

I was driving my galaxy i then had the coolant warning light come on with stop looked in rear view mirror and there was loads of white smoke. I stopped turned it off got towed home checked coolant and expansion bottle was empty so topped it up when it cooled down but it never over heated but did have smoke come out off expansion bottle so think head gasket. I've tried to start it again after a couple of days but it started to mis and smoke more or less straight away. Have took rocker cover off and where the injector rail plugs in is that the injector it self cos there is a large nut near the connection as i'm going to check for water in the cylinder first to see if it is the head gasket.

all help will be greatly appreciated :(