I've Had A Thick White Lotiony Discharge For About 4

I've had a thick white lotiony discharge for about 4 years now it's not really smelly only if I have my pantyliner for to long that's when it gets smelly. I don't have pain itching or burning but I have to put a pantyliner or else it will wet my pants. Once in a while my discharge changes to yellowish greenish color,I've noticed this twice now and the discharge is executive when this happens and still no pain itching or burning. What could it be ?