your symptoms of anal itching associated with white thread like structures clearly suggest that you are suffering from a worm infestation called as threadworms or pinworms
Treatment consists of ...
Taking a course of MEBENDAZOLE
( 400 mg stat one time ) to be repeated after two weeks.
Treating your entire family at one time,even if they are not having any symptoms.
You have to follow certain precautions so that re infection doesn't occur.These measures are...
Vacume cleaning of entire house specially bed rooms
Keeping your finger nails very short
Wahing your hands frequently .
( this is done so that eggs laid around your anus dont get under your nails during scratching your anus )
Avoid scratching your anus.
Take proper bath and wash your anal area well.
Whole precautions are to be taken for 6 weeks as this is the life span of worms in intestine.
Wearing loose underwears and washing your undergarments very well.
Avoid eating in your bed room so that eggs dont fall in your food from your bed sheets.
I hope it helps.