What is the meaning of...I sit on a snake head in my dream....?

Any snake in a dream could be a sexual symbol, and sitting on a snake head could have strong sexual connotations, regardless of the gender of the dreamer. The dream itself could have been triggered by simple hormonal fluctuations, or the subconscious might be alerting the dreamer that there are sexual nuances occurring in some aspect of life that the dreamer has not noticed. For example, someone might be making approaches at the workplace. It might be good to pay attention to what is "underneath" and unnoticed.