Let the pot dry out - the gnats, etc. thrive on wet soils and will disappear as the soil dries. It's a lily, it has a bulb which stores all it needs... watering, overwatering not only encourages pests, it encourages bulb rot. The big box stores, grocery stores, etc. selling Easter lilies don't know lilies from lilacs and water (over water) everything the same.

After it blooms, plant it in your garden where you will have more success with it rather than as a houseplant. Let it go through its normal cycle of dying back, stem browning, etc., and it should reappear next season although not necessarily in time for Easter since it's been forced into bloom. It'll revert back to its normal growth and bloom times.