Per the wiring diagram, the fog lamps receive power through the same circuit as the right low beam headlight. So it should not be possible for the fog lamps to be on at the same time as the high beam headlights. Also the fact that the fog lamps work seems to suggest that the problem is not with the combination switch.
The only thing that makes sense to me is that your low beam elements in the head lamps are burned out. You could check for voltage at the headlight connector. Left headlight is yellow/black wire; right is a yellow wire; ground wire is brown on both sides. If you have power there, the lamps are the problem.
In any case, water in the lamps means it is time for new ones.