l discharge but don't know what?

I have a persistent l discharge that i have had for about four years now. It is thick, white/light yellow, heavy and odorless. I have been to the doctors for pap smears and i always ask them to check for BV / STD's but always comes back negative, they say its probably my normal l discharge..which i know its not. I can sometimes see my cervical mucus through all this white muck and its getting to the stage where its unbearable. I have resorted to using tampons and pads because my underwear is completely white and crusty from this discharge and i always feel wet down there. If i have a bath i can see this white cloud of discharge coming out of my . I dont know what to do anymore i keep getting the same answers from doctors, and its hard to be intimate with my partner spontaneously because i have to wash down 'there' or it smells fishy during . Please help!