I'm not sure if I'm still in love with my wife.
Why do you think you're not in love with your wife?
We're not happy together and I don't think our marriage will last.
You have to talk with your wife about her feelings. The two of you may be able to attend counseling sessions to save your marriage. If you can't resolve your issues then it's best to end the marriage so that the both of you can find other partners to be happy with.
I don't think there's anything wrong with my life. I just don't love her anymore.
If that's the case then it may be time to end the marriage, but counseling will help the process go more smoothly. If you can't communicate with your wife, your marriage will end on bad terms.