All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
If your skin is naturally oily, without intervention from you, you are not required to wash it with soap before commencing your Wudhoo’ or Ghusl. There is no evidence in the Islamic Sharee‘ah that obliges the Muslim to do so. Thus, in principle one is not obligated to do something unless evidence proves it – and there is no such evidence in your case.
You have to know that whoever gives free rein to doubts will be dragged into obsession and incur undue hardship. One, therefore, may lose the sweetness of worshipping Allaah, so beware of that.
Allaah Knows best.