Sorry your not happy bro.
Have you really been miserable the entire 8 years? I understand the shotgun marriage, but you now have 3 kids, not 1. It is certainly possible for a married couple who are miserable to go from 1 kid to 3 in 8 years, but one or both of them would have to be pretty stupid for that to happen.
For that reason, I wonder if you have been legitimately unhappy the entire time. If you have been legitimately unhappy the entire time, my next question would be, 'Were you a lot happier before the marriage?'
There is no way for anyone to say whether you would be happier divorced. The only thing I would encourage you to do, before making any decisions, is spend some time thinking about what precisely is making you unhappy. Are the things making you unhappy related to the woman and the marriage, or are they something else?
I know a lot of people who got divorced because they thought they were unhappy with their marriage, but what they were really unhappy with was themselves and their lives. If that is what is making you unhappy, divorcing will not fix it. Like my sig says, 'No matter where you go-there you are.'
If what is making you unhappy is not related to the woman or the marriage, you should try to fix it within the context of the marriage.
If what is making you unhappy is related to the woman and the marriage, you can ask yourself another question, which is, 'Have I gone through considerable time, trouble, and effort to fix these issues, and come up short?'
If you can not answer that question with a yes, it is probably not time to get divorced. Usually, the time, trouble, and effort to get a divorce, then build a new life and achieve a modicum of happiness is considerably more than the energy needed to simply fix the problems you have. People sometimes get to the point where they are just kind of phoning things in and not making a real effort. Then things deteriorate a little, and the grass is greener mentality set's in.
If you and your spouse have not 'left it all in the cage' honestly, authentically trying to repair the marriage, then it is most definitely NOT time to get divorced. From your post, I'm not even sure you or your spouse have even got in the cage yet, much less left it all in there. You mention nothing of the efforts either of you have made to work on the marriage.
If you go through that entire process and still end up divorced, you will come out on the other end with dignity and pride. If you do not, expect to feel a great deal of shame and regret for sometime afterwards.