Other than eggs, nuts and peanut butter. are there any other food high in protein that can help you bulk up?

Yes: Unless you are already committed to a vegetarian lifestyle, you should consider meat in your diet especially if you are trying to build mass. Especially, peanut butter is loaded with fat and calories compared with lean chicken or fish, tofu or whey powder. If you're getting your health information from the internet, why not get a sensible scientific book or a dietician visit?

Protein with IBS: Yogurt, cottage cheese, milk, meat, fish, poultry, beans, soy, tofu. Whey protein is also excellent. You can purchase natural whey. Be careful about additives. Quinoa also is excellent protein. If you eat Quinoa, start with small amounts and gradually increase. Egg whites are BEST