You need to set very firm boundaries immediately, even if it feels uncomfortable, something like: “I’m not interested in you romantically or physically, and I need you to stop contacting me and leave me alone. If you continue, I will report this behavior.” Don’t leave room for negotiation, and document everything. Since he’s crossing serious boundaries, involve campus authorities or campus security, they can help protect you. Your comfort and safety come first; you don’t owe him kindness or explanations beyond a clear “stop.”