What software are you using? If you are using something like Audacity and don't have a degree in sound engineering that could be the problem. I have had the same problem in the past. I never was able to get the sound I wanted. I used Riffworks, Audacity and Magix Audio Studio. They were all too complicated to be of much use to me. I recently switched to Mixcraft 5 and have found it much easier to use and my music sounds 100% better.
Also what type of microphone are you using?
I have tried with that but I usually use Cubase.