One way to gain an understanding of your suffering is to install a suffering meter in your mind. As gauging suffering is not exact, a suffering meter can be a rough instrument. The most important thing about a suffering meter is not how precise it is, but how often you check it. Your suffering meter only needs to have a positive, neutral, and negative value, such as: suffering, nothing, and contented, or miserable, neutral, and joyful, or 1, 0, and -1. Simple.
Every time you check your suffering meter, also check your thinking and figure out just what you were thinking that inspired the reading on your suffering meter. That way you will see the connection between your thinking and your suffering. The more often you check your suffering meter and check in with your thoughts, the more likely you will catch yourself thinking up reasons to suffer. If you just watch your meter all the time, you may recognize the cause of your suffering and see the way out.
You can also use your suffering meter on others. When you notice somebody else is suffering, as they often are, offer them compassion and kindness. See what that does to your own suffering.