Your 68kg + 30 kg for luggage can't be the cause of your problem.
I weigh 107 naked, and any pillion would weigh quite a bit more than 30kg.
Wind resistance of the boxes may be part of it, and as others have said, check your steering head bearings. The wind input on the boxes may be unloading the front enough for looseness to cause the front end to wonder. Otherwise the rear shock would be suspect. Check it for compression while sitting still, and make sure the swingarm pivot bolt is tight.