I am 16 years old, 206lbs and my bra size is 40DD almost 40DDD. Would it be safe for a breast reduction?

I'm sorry to hear about the problems your disproportionately large breasts are causing you. It is probable that you are dealing with juvenile breast hypertrophy along with the physical and (possible) psychosocial consequences of this diagnosis. 
In my practice, timing of breast reduction surgery is determined on a case-by-case basis. It is not too early to do your homework and learn as much as possible about breast reduction surgery and the potential risks and complications associated with the procedure. Hopefully you have the support of your parents as you do your homework.
As you learn about breast reduction surgery, make sure you read about the potential risk/complications associated with the procedure. You may find the attached link helpful in this regard. For example, unsatisfactory scarring is one of the potential complications. Make sure you also understand that further surgery may be necessary in the future (for example if the breasts were to grow in size again).
On the other hand, breast reduction surgery is one of the most patient pleasing operations we perform and I think that for the right teenager (enough symptoms) it may be an excellent option (regardless of the age).
Sometimes breast reduction surgery is covered through health insurance. The best way to obtain insurance coverage for breast reduction surgery involves some “hoops” to jump through. The more documentation you have (for example, from your primary care doctor, physical therapist, chiropractor etc.) the better when it comes to obtaining insurance “authorization” for the procedure.This documentation and letter/pictures from your plastic surgeon will help you obtain authorization. When the time is right, seek consultation with well-trained/experienced board-certified plastic surgeons.

I hope this, and the attached link, helps.

Yes it is possible to do a breast reduction on a 16 year old.  As long as you have a parent sign the consent and you understand that there will be a scar on your breasts.  I use a medial pedicle  to keep the nipple sensation intact . I use special sutures that are all dissolvable and NO drains. It is on average a four hour procedure and you go home the same day. It it is a life changing surgery that you will make you very happy.  Always go to a Board Certified Plastic Surgeon. Good Luck,Andrew Cohen,MD

Thanks for the question.  First, you would benefit greatly from breast reduction, especially if you cannot get out of bed without there being severe pain.  You will, though, need parental consent since you are still a minor.  It is good that you have made your mother aware of your pain.All the best,Dr. JSB