About 2 Years Ago I Was A Vegan, Then Became

About 2 years ago I was a vegan, then became vegetarian, and now I eat everything. I noticed that since my diet changed, I developed a lot of gas. It makes me nauseous, spacey feeling in the head like the gas moves there, some shortness of breathe, and some chest discomfort. I am very constipated as well. I drink a lot of water and tea, chew ginger sometimes, and take simethicone chewable a almost everyday sometimes twice a day.