It's just one thing after another isn't it?!
Whilst trying to sort a knocking coming from the rear of my car (see
here) I noticed that when the car was being revved a fair amount of water was being spat from the tailpipes along with the occasional puff of what looks like white smoke.
This combined with the fact that in the last 8 weeks(ish) my coolant level has dropped from max - min is worrying me that it could be the head gasket.
However there isn't any 'mayo' under the oil cap.
Am i worrying unecessarily or is it likely to have gone?

Also are there any other signs that it would be showing if the head gasket has gone?