The condensation out of the exhaust is pretty mega at the moment due to the temp. Mine looks like a power station first thing in the morning!! When my headgasket went, I had no mayo, but loads of steam out the back even when the engine was really hot, but the main way I coul tell (excluding the compression test) was that water consumption was huge. A full coolant tank would only last 30 minutes before it was dry.
If your water level isn't changing, its prob just steam.