Whenever i go to the toilet or in general and wipe my vagina i see dirt like stuff (it's brown and almost like bread crumbs ) my labia majora also tends to itch . i have had a yeast infection before . please help me inderstand what this is ?

It could be just smegma because you have not watch your genital area quite often. You just need to watch your external genital organ with mild soap and warm water several times a week. Yeast infection usually causes burning urination and cheesy exudate besides itching. If it turns out to be yeast infection, you can try sitz bath with one cup of apple cider vinegar in warm water.