Can someone point me in the right direction?

I have a six-year-old female English Pointer who was spayed at age two. From being a few months old she has recurring episodes of shaking, lack of co-ordination, unable to open her mouth and chew food. When this first happened I took her to the vet who could find nothing amiss and seemed sceptical of my description of her symptoms. I contacted her breeder who said this had happened to one of her Pointers and it was low blood sugar and to give her something like a digestive biscuit when it happened. This is exactly what I have done when the episodes occur and have to put the food in the side of her mouth so she can chew enough to swallow. She then recovers.
When I moved about three years ago and my Pointer had symptoms again I took her to my current vet who did a blood test which was normal. I explained that I had just given her some carbohydrate so it may have been a false negative. Since then I have just followed the breeders' advice and treated her myself. The other day I took her to the vet again as she had developed a small lump in the chest area and her behaviour had changed in that she refuses to come out with me in the morning since the winter started and prefers to stay on the sofa and wait for me to return. In the afternoon she comes out as normal and runs and plays happily with my other dog.
The vet thought the lump which is fibrous may be trauma and to keep an eye on it. She was more concerned about the dog's weight which is 34kilos and to restrict her food and make her come out with me in the morning to increase her excercise. I reminded her of the low blood sugar problem and described her symptoms which she found "very strange" however she was not concerned about this and urged more exercise and diet.She suggested a prescription diet which i declined. When I got home I looked up hypoglyceamia in dogs and read that it is a serious and potentially life threatening condition. I would really appreciate some help here:
1. Controlling weight with my dog has always been tricky as if the carboyhdrate is reduced too much my dog has symptoms. I feed a mainly raw food diet of meat, chicken wings, liver, vegetables, and a wholemeal biscuit. Any suggestions please?
2. Am I right to assume her condition is low blood sugar given that she recovers when fed carbohydrate or should I have further blood tests having starved her and risk an episode of shaking etc?
Any suggestions or similiar experiences will be much appreciated!
Julie Capaldi, by email