The answer to 'why is my shingles leaking' is that there are several common causes, including improper installation, age and wear, damage from weather or debris, and poor ventilation. Symptoms may include water stains on the ceiling, mold growth, or visible cracks and curling in the shingles. Solutions can range from minor repairs to a complete roof replacement, depending on the extent of the damage.
If the leaks are minor and isolated, you may be able to fix them yourself by replacing damaged shingles or sealing problem areas. However, for more widespread issues or if you're unsure of the cause, it's best to call in a professional roofing contractor to inspect the roof and provide a proper diagnosis and repair plan.