Why did I get cataracts?

Causes of Cataracts. Cataracts are most often due to or made worse by (most common first): aging, genetics predisposition, excessive sun exposure, smoking, diabetes, steroid medication, previous trauma, inflammation, infection in the eye causing inflammation; previous intraocular eye surgery; other genetic conditions; can be congenital as well. You may have some of these risk factors. Your eyemd should be able to help.
Misdiagnosis? Cataracts can occur for a variety of reasons and at any age. It is just more commonly seen in patients over 60. Whenever you have a diagnosis that is a little unusual, it is not unreasonable to get a second opinion from another eye md. It is comforting if both give the same diagnosis, but if there are discrepancies, it'll give you the opportunity to look into this further before surgery.
Can be any age. Although we tend to think of the word 'cataract' as synonymous with old age, they can happen at anytime. Some children are born with cloudy natural lenses in the eye (cataract). Other factors like trauma (eg car accident) or steroids (eg. Inhalers) can lead to clouding of the lens at a young age. The good news is they are treatable and do not grow back. The surgery is very common and very safe.
Unusual . At your age, cataracts are very unusual, and caused by something, such as steroid use, chronic eye infection, genetic disease, etc. You should have a full evaluation to sort out the cause!