Here's at least a picture
of the sweater. You can check the pattern itself for the number and rows for decreases at the fronts, back and sleeves. They should match up or be very close. Make sure the you've done the decreases at the correct rows and that your measurements match any schematics that may be in the pattern (especially for fronts and back). If it all looks good except the sleeve length, you may have to rip back on the sleeve and figure out how to get the correct number of decreases into the length of sleeve cap that you need.
Come back with more questions if you need help with that.