I have a really bad phobia of dying and it's preventing me from sleeping at night. i don't know what caused it and how can i stop it?

Phobic about dying: You mention you have anxiety , and are already on St. John's Wort, + other 'herbals'. It sounds like it's time to schedule a Psychiatry consultation/ f/u, to get help with your current anxiety sxs. A common manifestation of anxiety is sleep disturbance, especially difficulty falling asleep. Your Psych MD will help you select a tx of talk therapy +/or medication that will be effective for your sxs.