2004 Toyota Camry losing antifreeze from reservoir

My 2004 Camry seems to have a slow leak someplace from the  coolant
reservoir tank. 145000 miles   new radiator last year. Sometimes  when i
drive esp when its  cold  or I accelerate from a stop i get an sound almost like  
marbles in a jar sloshing around. or  almost a pulley sound, its  subtle and  
had it for a yr off/on. I consume oil too i think from the  valve gasket
blowback, No white  smoking  and oil seems fine, car runs  OK  , concerned
about  poss small head gasket leak or could it be going into combustion
chamber , cant really afford to junk the cark  ( 4 cyl LE) , sometimes  it goes
away if add oil or  coolant.  no visible sign of leak,  Expensive to take apart to
diagnose?