If your earlier diet comprised largely of refined, processed or fibre-less foods, then your body, especially your gut, needs to adjust to the increased amount of fibre and complex sugars it is getting now.
It is important to include whole foods and their fibre in your meals, but the best way to transition is to increase the fibre-rich foods in your diet gradually and not all at once.
If you have just started including salads and other raw food in your diet, start with a small quantity and increase it as soon as you are comfortably able to do so.
Soak legumes (beans, lentils (dals), chickpeas (chana) etc.) well, preferably overnight, and rinse them thoroughly before cooking, to remove gas creating compounds. You could also sprout these legumes.
Water helps to soften and move fibre along, so do drink water whenever thirsty and increase your physical activity.
Make sure that you chew your food well and eat slowly while enjoying your meal.
Avoid carbonated drinks, chewing gum and synthetic sugar substitutes. If you frequently use a straw to drink, try just sipping straight from the glass.
Do have patience. Your body will gradually adjust to the increased amount of fibre and your gut will heal sooner than you expect.