Can u recommend what type of medicine to take or apply to cure whitespot on my body especially at my back? Thank you.

Tinea versicolor? Difficult to definitively diagnose without actually seeing it but most likely you have a condition called tinea versicolor. This is caused by a yeast (malassezia) that is part of our normal skin microflora. Otc treatments that may help include medicated shampoos like selsun blue and head & shoulders. Also antifungal creams like lotrimin (clotrimazole) af. If these don't help see a dermatologist.