Since you are not eating meat you may have Vit B12 and or Folic Acid deficiency. There are Balanced B vitamin supplements, you may find it necessary to take sublingual B12 (1000mg) with B6 and Niacin. B12 deficience can cause shortness of breath. It is also good to take Vit D3.
I don't think that the diet you are using gives you all the nutrients you need. Look at the Specific Carbohydrate Diet - I've found it helpful and it is gf.
Hope this doesn't happen to you again but if it does look at simple remedies for hyperventilation. Hoaehound is a good remedy for breathing difficulties and there are some cough drops and syrups available. I noticed recently that when I was taking hoarhound my breathing was easier.