This is the computer chair I use:
I'm a web developer who sits in this chair from morning until I sleep. Recently, I started to get back pains. I know I'm too young to have them. Can it be due to this chair? It's a small chair which doesn't extend up to my shoulders. Is it a good choice or do I need to change to a larger chair (which extends up to my shoulders) soon?
What you need is to get up every hour and stretch, regardless of whatever chair you happen to be sporting. Humans are not designed to sit in a chair 14+ hours a day, period.
It certainly wouldn't be helping any pain you're feeling. Having been through a dozen or so office chairs, the nicest one I've ever had has been a Herman Miller Aeron. Unfortunately it stayed with the office when I left the position. You need to look at the chair as an investment. even an expensive chair is cheaper than the medical bills you could incur from serious back problems later.
Look around at what's available; Herman Miller makes several different models at different price points, and they are well regarded as some of the most ergonomic chairs currently made.
