Hi dear, it’s never a good idea to go on a major diet during pregnancy. You already feel faint, possibly from dehydration, the hot weather, or low blood sugar. I think you don’t have to worry about your baby’s size so much at this point, especially if you don’t have GD. You can watch and see what happens during the next growth scan at about 32 weeks... for now, please don’t diet! Eat normally (all 3 meals). You don’t need to eat more than what you did before pregnancy for these meals.. in fact, it’s good to eat less per meal and eat more frequently in the third trimester to prevent reflux:) if you’re worried about baby being too big, eat normal amounts but healthier options.. less fried/fatty/sugary foods, more fruits and vegetables, lean meat, complex carbohydrates (wholemeal bread, brown rice if you’d prefer these). Don’t do extreme physical sports, but you can go for long walks to keep active:)
Don’t be stressed okay? It’ll all be alright:)