I second the folks at GT and what they said. Also, if at any time you actually have wrist pain from playing, something is wrong. If you have only been playing three weeks, the only thing that should hurt are your fingers as you build calluses on the tips of your fingers. Check your posture. My suggestion is this. Slow down to maybe an hour practice a day, or if you want to practice two hours, do like I do. I practice for 30 minutes take a short break, another 30 and a short break, another 30 and a short break and the last 30 and then stop till the next day.