If you don’t mind me asking, what testing did you have done?
I think symptoms vary from one person to another and abdominal pain and discomfort is one of the symptoms but mine has never been so severe unless it was to do with trapped wind or eaten a food with high concentrations of sugar like dried fruit. If it is related to the Candida then I can only think that you possibly have a very severe case.
What kind of pain is it exactly? Is it in your intestines and are there any other symptoms e.g. bloating, noticeable feeling of movements?
You said you were doing a no carb, low sugar diet but there are a lot of other foods that can still contribute to helping the Candida grow. You could try doing the cleanse as mentioned on this website. Because so many foods are cut out at that stage, if your symptoms disappear then you will be able to tell which foods aggravate your pain by slowly adding them back. I didn’t do the cleanse but that was because no one food makes my symptoms worse. Most foods have the same effect so just going with natural foods with no additives has made a difference.
Also is there anything else that you have noticed that makes your symptoms flare up? The worrying thing is that severe abdominal pain can be an indicator of a serious illness, but I would think doctors would be able to pick up on that.