God is just, and one day all those who have ignored God and disregarded His laws will stand before Him and receive what they deserve. The Bible warns, "But they will have to give account to him who is ready to judge the living and the dead" (1 Peter 4:5).
Why do some people seem to go through life without any problems? Frankly, I don't know the full answer to that; God sees the whole picture, while we see only a part. Someday we will understand when we go to be with God in heaven–but until that time, we know that because God loves us He can be trusted, even if we don't understand. As the apostle Paul wrote, "Now I know in part; then I shall know fully" (1 Corinthians 13:12).
I can't help but sense from your letter, however, that you may have allowed bitterness or resentment to creep into your life–and if so, I pray that you will turn to God and ask Him to remove them. More than that, if you have never asked Christ to come into your life and forgive you for your sins, I pray you will open your heart and life to Him today.
Yes, sometimes life seems unfair. But when we focus on Christ and not our circumstances we begin to see life from a different point of view. Make Him the foundation of your life, and your problems will begin to fade.