Persoanlly, I'd top the levels back up, and start again, keep checking it every few days, see if you can see any marked or noticeable drop.
We were always taught to fill fluid levels to the maximum mark, which incidentally, gives you a little more leeway when it comes to your weekly routine.
Take her for a short 5 mile run, just to get her up to temperature and water pressure etc, and place a nice new large piece of cardboard box under the engine bay. Any water or oil leaks will show up.
If it's burning oil, this would be indicated with blue smoke. Get a mate to follow you, and give the car a bit of work to do, find the steepest hill in your neighborhood and make the engine work.
If it were head gasket, i'd expect to see one of three things. Oil in the water, water in the oil (white gunk) or steam out of the exhaust.
Don't confuse the steam out of the exhaust with condensation at start up though. (although in this heat, i wouldn't expect that)