A 28-year-old man from Mumbai presents with a 3-year history of intense fear of blood and injections. Whenever he sees blood or anticipates an injection, he experiences dizziness, nausea, and a sudden drop in heart rate and blood pressure, often resulting in syncope. He has avoided medical checkups and dental visits for years. His fear is recognized as excessive and irrational, but he cannot control it. There is no history of panic attacks in other situations, and his anxiety is confined to blood/injection-related scenarios. What is the most likely diagnosis?