my 6 week old has been nursing constantly lately and one of my nipples has become sore. it burns and is tingly when he is nursing. the other side is not sore at all. so im worried it might be thrush. how do i tell the difference? his tongue is whitish but it just looks like it always has. how long of soreness do i wait until i go to the doctor? the pain isnt so horrible that i cant nurse. i try to stay off that side but i can stilldo it.