Is your car overheating?
I blew 2 head gaskets on my old car..............was caused by water seeping out of a crack in the head of the engine, or so the mechanic told me. He didn't charge me for the second gasket replacement because the head integrity check he ran beforehand failed to pick up the crack. Either that or he was trying to rip me off.
Anyway, to answer your question, one possible cause of a head gasket is caused by overheating, which in turn could be caused by something else. (In my case a crack in the head). A head check could be in order for you.