I have experienced for years a similar problem with my 8 year old son who is still terrified of being kidnapped after the Maddy Mccann situation. Prior to this he was always a good sleeper. Since then I have tried everything to get him to sleep through the night without waking us and to go to bed without us going up every 5 minutes. For many months he would not even be downstairs on his own either. The amount and length of disturbances would vary depending on the level of fear at the time.
This is what has worked for us:
Star charts did sometimes but sometimes the fear would be greater.
A bed in your or a siblings room does work but after a few months we realised this would be a long term thing and not good for him or us in the long run. To be honest he would still do this now if given the chance. I wouldn't recommend starting this up or sleeping in your bed. It is a hard habit to break.
A worry book in which he could write down his fears and then close up to take them away. He still uses this tactic but again it is not effective all the time.
We realised that the more we shouted and told him to go to sleep or showed our frustration with him in any way whatsoever, made the situation 10 times worse and was guaranteed to make it a lot harder and a longer night for us.
We always put him into bed and always refused to stay with him for any length of time. We always promised that we would go back in within 5 minutes whether this was bedtime or the middle of the night. Sometimes we would only go in a couple of times sometimes more but he had to trust us that this would happen and showing our frustration would mean it would go on far longer. Talking was kept to a minimum and fears discussed in daylight.
MOST IMPORTANTLY
We eventually discovered (and this was the secret to virtually solving everything) Why oh why did I not see the link before! It would have saved us years of sleepless nights.
A vicious circle emerges.
He is tired and therefore worries more which wakes him up several times through the night. He therefore is even more tired which exacerbates the problem and so on.
Now I have realised this, I can break the cycle immediately it starts up by sending him to bed earlier (daughter has to pretend to go to bed at same time and then come down again) and being very calm and understanding and going in every 5 minutes in the night. Within a couple of nights we are back to ok again whereas before that it would last a long time before we had a less afraid period and less disturbed nights.
Hope this helps. We tried treating it as manipulative behaviour early on in our experiences when the softly softly approach didn't work and tried to be hard with him but the fear was genuine and the only thing that minimised the fears was the above. Believe me I tried lots. I really wish you well because when you are tired yourself, it is really difficult to be so patient in the middle of the night.
P.S The doctor was out of order.