Thanatophobia Destroying My Life

When my son was born two years ago I started to become afraid of dying,the thoughts of not being there for my family makes me feel terrified and not knowing what happens after death terrifies me also.  its progressively gotten worse over time and recently Ive started having panic attacks and uncontrollable bouts of crying. I feel detached from general life and I seem to be unable to be happy on any level. Its ruining my relationship, my business and my ability to look after my children. I dont know what to do or were to turn too. I feel like my partner,friends and family don't  fully understand how I feel and this makes it even harder. I need to get better for the sake of my kids but I dont know how...