Blown HG results in overheating sometimes loss of heat and Milky Oil. Check your oil if its milky white then you have a Blown head gasket.

you usually dont see a loss of power like that with a Blown head gasket unless your loosing assloads of compession and in that case id say cracked head.
What codes were thrown if any ? Is it missing at all ? When was teh last time you git gas ? how low on fuel were you in teh tank... Did you drive through any puddles or anything ?