First, you should know you're not alone...look at all the responses you've received! Second, you should be proud of yourself for even getting back into the water after a traumatic event. Don't expect to overcome it quickly and easily, especially considering that a trauma, by definition, is an emotional wound or shock that creates substantial lasting damage to one's psychological development, often leading to neurosis. Aaagh!
I have also had some dive trauma, specifically doing mask-clearing during my O/W check-out dives. Although mask-removal skills were easy in the pool, it was a whole new situation in open water. The first time I tried, I started to panic as soon as I filled my mask full of murky quarry water. I began hyperventilating (it just seemed like I couldn't get enough air out of the regulator and I was sucking so hard I could hear and feel the regulator going "bump, bump, bump" which further freaked me out). In my rising fear I thought maybe something was wrong with my regulator so I grabbed my alternate, forgot to purge, swallowed water, and then found the alternate wasn’t giving me what I thought was enough air either. By this time I was beyond returning to a calm state. I bolted for the surface and fought my DM the whole way. The had to tow me in and about ten minutes later I threw up in the restroom. Very impressive. They said I was the second worst panic case they'd seen (apparently I calmed down when I got to the surface but the first place diver -who is now an instructor by the way - continued to panic all the way to land).
I came back the second day and did the same thing, only this time, in addition to everything I'd done the day before, I also tore off my mask, and threw the regulator out of my mouth on my way to the surface. Fortunately another group was doing rescue and recovery training so they got my mask for me.
So, I spent one night a week for two months in the pool and then tried for my O/W certification again. This time I was with a group and as soon as I started feeling panicky I didn't bolt. Instead I told one of the instructors I had to go up and we ascended slowly and responsibly. In retrospect I think the only reason I didn't bolt this time was because I didn't want to ruin the experience for the other new divers waiting to clear their masks (hey, whatever works). I was alone the first two times so I could be selfish.
Anyway, after my third attempt I gave up. Diving was something I'd always wanted to do but I just didn't think I could do it. As I loaded my gear into my car I was crying uncontrollably. The dive shop owner came over, hugged me, and said, "Come back tomorrow and I'll work with you. Give it one more try." I thought, OK, one more time...
We spent about 45 minutes with me just sitting on the platform at the quarry in about five feet of water. I practiced sitting there with no mask and then holding my breath as long as I could before slowly breathing out little bursts of air every few seconds before I stood up. I think he was trying to get me comfortable with the feeling of the cold water on my face and then trying to show me that even without an air source I could safely ascend from 25 ft. We took baby steps until I could easily remove, replace and clear my mask while I was sitting there. And the entire time my DM had his hand reassuringly on my shoulder (because anything could happen in 5 ft. of water!). I asked him, "Should we try it now?" and his response was always, "I don't know. You tell me." His patience was endless and this was exactly what I needed.
At 25 ft. before I started filling my mask my DM put his hands on my shoulders and looked me straight in the eyes for about five seconds as though to say, "I've got you. Nothing bad will happen." At first it took me about five minutes to clear my mask because I had to take so many mental breaks to calm down and slow my breathing before I could blow out more water. But, once I got half the water out and opened my eyes, I could see my instructor's totally calm eyes smiling at me as he slowly (and patiently) nodded with encouragement. This was exactly what I needed. I got my certification that weekend.
And, although I was able to do it, it wasn't easy by any stretch. Even when I was down there with the group later that morning, I couldn't do mask-clearing when it was my turn in the line-up. The DM would then wait until the group was moving to the next set of skills and work with me by myself.
So, I think I have a good idea of what you're going through. Based on my experience I think the advice you're getting here is right on point. Work with an experienced instructor who has the patience and commitment to stick it out with you. I have no doubt that I wouldn't be diving right now if I didn't have the good luck to have such a great DM. And, as you can see from my name, I am even joking about "my" trauma now. I think going through all this will make me – and you - better divers. Even though it won't be easy I
will get so good at mask clearing that I can do it without even thinking.
Stay with it. Go slowly (even if that means sitting in the shallow end of the pool blowing bubbles for hours and hours) and, most importantly, find the right support. Find an instructor with tons of experience who has worked with "special" students (as I like to call myself).
I know you can do it. Don't give up! And, remember, challenges are what make life interesting; overcoming them is what makes life meaningful.
