3 hr glucose 3 day prior diet had me feeling ill?

Hope • Baby girl 08/05/15 Baby boy 11/28/18

Is this normal? As stated in a prior post, I have to take my 3 hr glucose tolerance test on Saturday so today I started the 3 day diet instructions.. 150 extra carbohydrates per day.. I have gone through breakfast and lunch and my body is feeling awful that I cannot even think about dinner tonight. I am feeling run down and exhausted and just overall ill.

Should I be feeling this way? Is it normal?

Side note: This diet is way more food than I am used to eating in a day as is. Everyone said I would love being pregnant because I can eat a ton, yet this whole pregnancy no matter what I eat I get full quickly and feel ill. This is a more extreme ill feeling than that however and I am seriously dreading the next two days of this diet.