First steps in self-hypnotherapy

I am currently working my way through Adam Eason's book, The Secrets of Self-Hypnosis: Harnessing the Power of Your Unconscious Mind. This was recommended to be by hypnotherapist Phil Mattingly, who is an old acquaintance. 

I know that I should be able to achieve self-hypnosis. Many years ago, in my first year at university, I followed a self-hypnosis script in a magazine and managed to put myself into some sort of trance; I relaxed by imagining myself sinking down in an elevator, going down floor by floor, and regressing in time as I did. When I opened the elevator doors at Floor Zero I imagined my parents' house as it was when I was four years old, and was able to walk around looking at objects and bits of furniture which they had got rid of many years ago and which I had completely forgotten about. It was fascinating. Then someone knocked on the door of my room and I came up out of the "trance" as though I was coming up through water towards the light. 

Adam's book describes a model that you can use to help put yourself into hypnosis. So far, I have just about memorised this model and am just beginning to try to use it. However, I know I need to be careful. There are various traumatic things that I have experienced in the past and I don't want to experience anything to do with these. I suffered from severe PTSD for a long time and after therapy was able to accept but not resolve some things. I am a bit scared as my first atttempt at self-hypnotising had me remembering something I would rather not remember, so now I am wondering if I should seek the help of a hypnotherapist to get me started safely.

I am currently awaiting the results of a CT scan that I had last week, and it's impossible not to feel anxious about this (cancer patients call this "Scanxiety"!). If it's good news, I'll have another three months free of treatment and will be able to plan a really good Christmas to make up for the last one being so horrid. If it's bad news I'll have to start chemotherapy again and face all the shit that involves. Losing my hair a second time will be difficult, I currently have a couple of inches and really appreciate having it. So, either the news will be utterly wonderful or utterly crap - there is no middle ground - and I will have to have these scans every three months for the rest of my life so I really hope I can use self-hypnosis to help me cope with this.