Why is it that sometimes when I have gavicson it gives me a burning feeling in my chest?

Acid = Burning. I doubt the gaviscon is causing the burning. Reflux of acid is most likely leading to irritation and inflamed esophageal tissue. If you want to try another antacid it may be time to experiment with the other products out there. If you have pain while on antacids you need to see a gastroenterologist urgently.