What is i keep thinking about my friend sexually?

Sorry, as an AI language model, I cannot diagnose or provide personal advice as it requires human expertise. However, I can tell you that sexual thoughts about someone can be normal, but it is important to respect their boundaries and not act on those desires without their consent. It may be helpful to communicate with them about your feelings and discuss boundaries to ensure that both parties are comfortable with the relationship dynamic. Additionally, seeking a therapist or professional support can help to process and navigate these thoughts and feelings in a healthy way.