Do the stock prices always move with market news/speculation? Why do stock prices fluctuate so much?

Demand and supply factors are the drives of stock prices. But as to what affects demand and supply forces, there could be a whole range of them. Stock prices will move in as much as demand and supply forces are at play. News, speculation, earning reports all affect stock prices since demand and supply forces are influenced by them.

However, there are many other forces that affect both demand and supply. You will probably have to look much closer at what's occuring to get a better picture of how much share prices will go up or down.

The most important thing to realise about stock prices is that it's less to do with how the company is doing financially, and more to do with how the market participants perceive the company to be doing. So yes it is affected by news, as news affects emotion, and emotion leads to action - that is, to buy or sell.

The fluctuation that you see is the result of different bids to buy and offers to sell, and related metric to look at is trading volume, which will reflect how 'real' those bids and offers are.