Hi Paul
Have a look at the Sticky Threads section - the diet I use is on there - Viv's Modified Atkins Diet . As posted, it is a weight loss diet, but it gives you a basic list of foods you can eat that contain minimum carbohydrates - quantities unlimited if you don't need to lose weight!
Then get yourself a carb counter book (eg Collins Gem Carb Counter), and add in additional carbs to your liking, from those that are lower carb and Low GI. You can find the Glycaemic Index lists of foods on the web - I think you can even get an App, these days.
Dr Atkins would be turning in his grave to hear me recommend his diet to keep your weight up, but I see no reason why it shouldn't work, eating a high calorie but controlled carb diet, to keep your weight on. You really can't do it without eating fat, though - just make sure it's good quality, unprocessed, and as natural as possible. No baked goods, limited ready meals. Always read labels. You may be able to tolerate some bread every day - Burgen, or multi-grain wholemeal. Grazer, one of our regular posters, can manage Shredded Wheat for breakfast without spiking his blood glucose too much. Some people can cope with porridge.
I might add that my blood pressure and cholesterol readings have never been better than when I'm eating 'Atkins'. My BGs are now rarely out of non-diabetic ranges. But I do still have plenty of weight to lose.
The main thing is, eat to your meter. For now, test before every meal and then 2 hours after. If the food is "safe" for you, the second test should be pretty much in line with the first.
It should be worth a try!
Viv 8)