It seems my gold resets to 0 every time I reach 100 coins. I can confirm this because I had 90 gold in my inventory and then sold something and my gold count changed to 12. I noticed that my gold was always lower than it should be, but I don't spend any significant amounts. Is it being stored elsewhere? I don't see it in the bank anywhere. Is it just a visual glitch? Any help would be appreciated.
Guild Wars 2 has 3 levels of the main currency: Copper, Silver, and Gold. Most likely you're reaching 100 copper coins and they're being converted into one silver. This happens automatically, so that might be where the confusion comes from.
You can look at this article on the guild wars wiki for more info on how the coins work.