Is it true that illness or problems in my life are because of my sin?
If that were true, who would be healthy? Furthermore, what sins have the starving children in third-world countries committed? The answer to your question is a resounding, NO! You face illness and problems in this life because of the fallen state of this world, not as personal judgment.
However, there are sometimes painful, but natural, consequences to your sin. If you have pre-marital sexual relations you may contract a disease. Is that a curse that God sent to punish you for your sin? No, it is a natural byproduct of an extremely unwise decision. If you smoke cigarettes for 30 years and then develop lung cancer, is that God’s fault? It says right on the package of cigarettes that it could happen.
God never made a promise that if Christians live good lives, their lives will be perfect. In fact, the opposite is true. Furthermore, God says that we are to take joy in our pain because, through it, we are being perfected. James 1:2 says, “Consider it pure joy, my brothers, whenever you face trials of many kinds, because you know that the testing of your faith develops perseverance.”
When you face a difficult time, draw close to the Lord. Ask Him for relief from your burden. He may not remove it, but He will surely help you carry it. In Matthew 11:30, Jesus says, “Come to me, all you who are weary and burdened, and I will give you rest.”