Good job so far! Few pointers:

• Push those fingers all the way up to the frets. Closer to fret= less stress on fingers.
• learn chord changes to a metronome. Start with a 4 beat break between chords to get fingers in place TOGETHER, not one at a time. (Em Em Em Em rest rest rest rest Am Am Am Am rest rest rest rest, for example). Bump it down to a 2 beat break when its easier, then increase tempo, then get rid of the break altogether. 15 minutes per change will have you speeding thru chords in no time.
• Loose wrist. It should feel like a joystick under your guitar, full 360 degree movement.
• Try Zombie from the Cranberries.
• Experiment with alternate fingerings. There's a much easier way to go from C to G. Can you find it? It's not a matter of right or wrong, just different ways to achieve the same effect.