My four-month-old macbook pro's battery when fully charged is now down to 2 hours life from 7...in the last week. Why?

Question

I bought my macbook pro 13" about four months ago and have been in love with it ever since - especially as compared to my old PC laptop, the battery stays cool and lasts forever when I am working. Best charge was 7 hours. However, in the last week I have noticed the battery suddenly becoming hot when I unplug the charger, and the best length of time I can get on a full charge is 2 hours.
I have made sure all the settings are for prolonged battery life - which they've been since I first set up - and turned off all programmes running in the background, but this has not made any difference. I have been using iMovie a lot lately which takes a lot of battery which is probably why I didn't notice the battery being low as it automatically seems to make the battery slump to 2 hours when it's on. It's off now, and my battery won't improve.
I have also now followed the instructions (below) about calibrating, but this has had no effect. My housemate bought the same model a month ahead of me, uses it probably slightly less, but his is still 7 hours for a charge.
Is my battery faulty?
Calibration instructions used:
PowerBook G4 (15-inchDouble-Layer SD), MacBook (all models), MacBook Pro (all models), and MacBookPro (17-inch) (all models)
Thebattery calibration for the PowerBook G4 (15-inch Double-Layer SD) and anymodel of MacBook or MacBook Pro has been updated because of a new batteryreleased with this computer. With these computers, follow these steps tocalibrate your battery:
Plug in the power adapter and     fully charge your PowerBook's battery until the light ring or LED on the     power adapter plug changes to green and the onscreen meter in the menu bar     indicates that the battery is fully charged.
Allow the battery to rest in the     fully charged state for at least two hours. You may use your computer     during this time as long as the adapter is plugged in.
Disconnect the power adapter while     the computer still on and start running the computer off battery power.     You may use your computer during this time. When your battery gets low,     the low battery warning dialog appears on the screen.
At this point, save your     work.  Continue to use your computer; when the battery gets very low,     the computer will automatically go to sleep.
Turn off the computer or allow it     to sleep for five hours or more.
Connect the power adapter and     leave it connected until the battery is fully charged again.
Tip:When the battery reaches "empty", the computer is forced into sleepmode. The battery actually keeps back a reserve beyond "empty", tomaintain the computer in sleep for a period of time. Once the battery is trulyexhausted, the computer is forced to shut down. At this point, with the safesleep function introduced in the PowerBook G4 (15-inch Double-Layer SD)computers, the computer's memory contents have been saved to the hard drive.When power is restored, the computer returns itself to its pre-sleep stateusing the safe sleep image on the hard drive.

Answer 1

Thanks Sig. The information is here: Anything useful stand out?
Battery Information:
  Model Information:
  Serial Number:    9G1130CJVD3MA
  Manufacturer:    DP
  Device Name:    bq20z451
  Pack Lot Code:    0000
  PCB Lot Code:    0000
  Firmware Version:    0201
  Hardware Revision:    0002
  Cell Revision:    0158
  Charge Information:
  Charge Remaining (mAh):    5663
  Fully Charged:    Yes
  Charging:    No
  Full Charge Capacity (mAh):    5663
  Health Information:
  Cycle Count:    59
  Condition:    Normal
  Battery Installed:    Yes
  Amperage (mA):    261
  Voltage (mV):    12574
System Power Settings:
  AC Power:
  System Sleep Timer (Minutes):    10
  Disk Sleep Timer (Minutes):    10
  Display Sleep Timer (Minutes):    10
  Wake on AC Change:    No
  Wake on Clamshell Open:    Yes
  Wake on LAN:    Yes
  Current Power Source:    Yes
  Display Sleep Uses Dim:    Yes
  Battery Power:
  System Sleep Timer (Minutes):    10
  Disk Sleep Timer (Minutes):    10
  Display Sleep Timer (Minutes):    2
  Wake on AC Change:    No
  Wake on Clamshell Open:    Yes
  Display Sleep Uses Dim:    Yes
  Reduce Brightness:    Yes
Hardware Configuration:
  UPS Installed:    No
AC Charger Information:
  Connected:    Yes
  ID:    0x0100
  Wattage (W):    60
  Revision:    0x0000
  Family:    0x00ba
  Serial Number:    0x00262704
  Charging:    No