I'm applying selsun blue 1% ss & clotrimazole 1% how long till the pityriasis versicolor desapears?!

See a dermatologist. First, it is always possible that the diagnosis is incorrect. However, some cases of pityriasis versicolor don't get better with topical meds. And some patients have a predisposition to get the condition and not clear it well. Seeing a dermatologist will allow you to come to a solution.