Your fingers will definately feel sore if you are just starting to play the guitar. Like everyone has said here, that is very normal. If you have been playing a while and have developed the calluses, this shouldnt be happening anymore and i would think you are pressing to hard. There is only a certain amount of pressure needed to be applied when playing anything on the guitar. The best way to determine if you are pressing to hard is lightly rest your fretting hand finger on the string you are going to play so that it is muted. Repeatedly pick the string you are muting while slowly pressing down the string with the frettin hand finger until the sound becomes clear. You will notice that it does not take alot of effort at all to make the string ring clear. Unless you have really low frets and an old guitar. That might also be an issue.

And also, as a general rule. Do not practice technique for more than 3 hours a day. You are prone to injury, and as guitarists, thats definately somthing we do not want.

Hope this helps. :)