Yes, I was charged the fee when I bought. Now I'm waiting for price to hopefully go up. If it does that and I sell, will I be charged an additional fee?
Normally, every time you execute an order (every time you sell/buy), a fee will be taken from the amount you are buying/selling.
But... you need to understand how GDAX fees work. Passive orders (maker) has no fees. While active orders (taker) has a fee of 0.30% (until you trade more than $10m, then your fees will get better);
If you don't know the difference, read this:
https://www.gdax.com/feeshttps://cryptocurrencyfacts.com/maker-vs-taker-cryptocurrency/TLDR:
Every time you place an buy/sell order that is executed immediately (i.e you are buying/selling at the market price), you will be charged a fee of 0.30%;
Every time you place an buy/sell order that isn't executed immediately (i.e you put an order to sell 1 BTC at a higher price than the market's price, so it takes some time to get executed), you won't be charged anything.