Lizzi, I have a few concerns for you here:
1. You have experienced an extremely unpleasant incident, which is obviously still haunting you despite some 18 years having passed; and
2. You are in control of a vehicle whilst (I'm only basing this statment on what you have said) you are obviously not in mentally fit state to do so. Now, I'm probably going to be a little harsh over the next few paragraphs, but I have some good suggestions for you which will help you get back "on-track" again! I must warn you of some serious dangers, though.
I will just qualify this post with the fact that I was an Advanced Driving Instructor in the UK, teaching people to drive to the same standards as the police (without high speed persuit, of course!). I hold licences for numerous vehicles including cars, trucks, motorbikes, helicopters and aeroplanes!
I'm sure that you have received professional counselling, but perhaps you need to consider going out with a driving instructor for a few lessons, just as a refresher course, which will help build your confidence again. I fully understand how traumatic this situation is for you, and I wouldn't want to make it any worse, although I would like to share the following facts with you.
There are 3 main categories of driver. There are those who drive too fast, and those who drive normally. The third category can be just as dangerous as the first, however, it is not as clear-cut. In cat 3, you have people who are nervous, spatially unaware, distracted, or just simply slow.
All the road regulations are designed to allow the majority of people to be able to drive, however, as we know, there are those who should not be on the road. If you drive too fast, your reactions may not be quick enough. If you drive too slow, you hold traffic up, and people naturally become impatient, making them become worse drivers.
My biggest concern lies with "nervous" drivers. When you are nervous, you are easily distracted. The feeling of nervousness is a distraction in itself. Driving a vehicle requires that you be alert and reading the road at all times. Failure to do this, can be catastrophic, as well you know. Whilst you may not hit somebody, you are more prone to make mistakes. This in turn is more likely to cause someone else to make a mistake, which could hold serious consequences for either that, or another person's wellbeing.
By turning on your ignition, you are making a legal statement that you are in good enough health, both mentally and physically, to operate the vehicle safely. From what you have said in your post, it suggests that you are not. Driving when you are "so anxiety filled..... ....that you just can't do it..." is just as bad as that driver who drove drunk. It is not fair on you or other road users.
Now the good part! You have not mentioned any further incidents in your post since the major incident. I'm therefore making the presumption that since then, you have not been involved in any other incident. If I'm right, then this is good. If I'm wrong, then all the more reason to act on the following:
I have been witness to numerous, and on two occasions involved in (which were not my fault, and also unavoidable), accidents. I have witnessed a number of fatalities. It is quite natural to think "what if I'd done something different... would it have changed what happened?". This is a thought which is probably still at the back of your mind, along with the fear of having to see something like that again. There are a number of professionals around who specialise in debriefing for these events. I am guessing that the anxiety hits as soon as you know you have to drive somewhere. This is a symptom of Post Traumatic Stress Sundrome (PTSD). Whilst you may not have it, it would seriously be worth checking it out with a suitably qualified Psych Med Practitioner. There are many things that can be done to help you recover properly these days!
My final suggestion is to take a refresher course with a driving instuctor. An advanced course is preferable, if available in your country. I do this as a matter of course, generally every 5 years. There are always new rules and regulations, even new signs! It just makes sense to refresh yourself with the rules like this... if only it were compulsory! I digress... This also serves as a confidence boost for anyone who is nervous. If you can jump in with an instructor, without having to worry about sitting a test, then you can relax, and just learn without any pressure. An instructor will obviously be able to pick up any faults you have, you can work together to correct them, and once you're done, if your instructor says "Excellent! You're driving is absolutely fine!", then you know for a fact that you are a good driver.
Please remember though, whether it be stress, alcohol, drugs, loud music, anxiety, medication, kids, or otherwise, a driver that is distracted for any reason should not be on the road in the first place (in an ideal world!).
Good luck in your recovery, and safe driving.
~Matt
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