My back is aching now that i stayed longer in front of my computer.Do u know?

Could be the angle you are holding yourself in, sometimes if you don't let the chair support you and tend to sit up more, this will cause your back to ache. Place a pillow along your lower back, this will help give you added support. If you feel the aches coming on a little stronger, you might want to consider putting either some heat or ice on the area while you are sitting at your computer as well. If you are at home, first put ice on your back for about 20 minutes. Then do heat. Moist heat is best because it penetrates the muscles. An easy way to do so, take a bath towel, wet it down, then stick it in the microwave for about 5 minutes, take another towel, place it against your skin, then place the hot towel, this should help keep you from getting burned. Oh, don't forget to ring out the towel a bit, that way it doesn't soak you down. You could also stand up and do a few light stretches to help keep the muscles loose.

I switched computer chairs the other day. Now the problem I have is my butt going numb. It is not a very comfortable chair, but it has wheels. My other chair did not have any wheels. I think I am going to have to switch back though.