Anyway, back to armchair analysis. If you've chosen your aikido practice as the path you are going to trod to find a way "around" the block which is the touch problem, since touching is inherent in aikido practice for skill progression, you've rather deliberately set up a challenge structure for yourself, wouldn't you say? I think so, & I applaud you for doing so. You did say it was about 15 years ago that the event took place?
The touch problem is a symptom, right? The touch problem isn't the actual "problem," it indicates that the real "problem" exists, the psychological trauma of the attack. I tend to agree with the PTSD concept above. PTSD can be immediate and debilitating, or it can be... subtle and sneaky, it doesn't have to manifest as hallucinations like the movies. Vague fears, depression, anxiety all can be there. Seen that both in war vets we picked up, as well as in fellow paramedics, firefighters and cops I associated with during that life period.
I AM going somewhere, sorry for rambling nature of the post. My colleagues in emergency services, the ones who were suffering from "burnout" - that's what we called it at the time, us young (i.e. stupid) ones - som
e of them ended up finding a psychologist from the local Veteran's Administration hospital (Michael E. DeBakey VA Medical Center ). She had been doing work for some of the repeat business customers we had with those problems, and things worked to bring some of those guys in contact with said therapist. Long story made short, after working with a couple of our, what I'd call hard cases, perhaps 6-8 sessions, those two guys were pulling out of the bad place they had found themselves in.
I'm not drawing parallels in situations suffered by you vs. those found fighting fires, etc., but people react to stressful life changing experiences .... not similarly, perhaps, but their experiences tend to shape them in a similar way. I hope I said that right. I would suggest that it might work very well to take advantage of all the advice given here in kind spirit, combine them into a method which allows you to both seek a kind, professional counselor who can start working on the underlying issues, while at the same time find a kind soul or two with whom you are the most comfortable at your dojo, and speak to them privately, and also to your sensei, and explain what it is that you are working through.
I don't know if the following would work or not, but we use it all the time to work towards a difficult skillset with our people. Progressive overload theory. If, for example, you took an average beginner student, with no formal training and no concept of any martial art, brought them into a dojo and suited them up, and said - "We are going to practice multiple attacker defense today, and yu are first up." Probably wouldn't work out well, would it...
No, obviously not. So, we work up to it. I know, sounds obvious again, but I'm going somewhere. In multiples, the way we do it is start with just 2 "attackers" and we have them limit their attack to only trying to grab the right hand of tori and "control" it. The defender's/tori's task is to move, execute a certain releasing motion (and only that one motion is allowed for this level of exercise), then the other attacker also grabs the same hand, repeat release, etc. over and over and over. Say 3 minutes of that, to get everyone moving, but in a very controlled state.
Stage two is a choice for me, or whoever is running that drill. Keep the right hand grab and now allow defense with either of two releasing movements, or, keep only the one allowed releasing technique and allow the attackers to grab either the right or left wrist. You've increased the options, thus the complexity, exponentially. Granted, only an exponent of 2, but if you do that again by adding the option you didn't chose, you can see how the doubling effect works on the chaos.
So, applying the progressive overload to your own aikido practice, maybe something like this would work as a direct training mechanism to "take on" the touch anxiety.
Take a technique you are comfortable with performing, and do it with the attacker several times without stopping, moving more and more naturally from a formal kata mode into a more rndori mode. Then, YOU ask your attacker to increase the intensity of their attack in some way which involves slightly more physical contact, but still allows the same technique to be performed on your part, e.g. in my own Tomiki curriculum, there are the releasing movements, which are learned as a beginner just against the attacker grasping the wrist and not "doing much" with the wrist but holding it. But... what if they grab it and pull you towards them? Release movement/technique still works, though the directions and vectors change somewhat. Next would be, let's say it is a cross-hand grab. Add to the right-to-right crosshand grab,, the attacker's left hand also grabbing at the wrist, and when that's no problem, work up to the left hand controlling the elbow (or attempting to do so) Work the left hand up your own body slowly, keeping your own "discomfort" level where you can handle it without the lock-up you describe above. Eventually, you will get to where uke's attack comes in, grabs your wrist, and yanks you through to apply a choking technique on you from behind. THAT is not going to be comfortable, but you can see how you would get there, I'm sure, and also, how in the controlled setting, you could work up to that sort of thing in a slow, steady progression which you control. I doubt it will be fun.
But, working on the aikido stuff would be a symptom, again, that the work you are doing, either with a therapist/counselor, or on your own with a support group of friends and training partners, is working.
I don't know if any of the above is helpful, or not. If not, just ignore, but I do hope it pulls some things together in a practical way for you.