Toasted sesame is not recommended for OP. Although I used it the first couple of times when I started a year ago until i could get to the store. I don't remember my teeth being stained from it.
Olive oil has been reported to stain teeth as well but I never noticed it. The best for whitening seems to be coconut oil.
Are you sure your teeth haven't lightened to the yellow stage? Sometimes we don't notice coffee or tea stains until they start to lift.
Are you doing a search in the archives? There's lots of good info stored there.