When I was 130lbs my bra size was 34B. Now I am 220lbs and I wear 40D. Will my breast size reduce with weight loss?

A large
amount of weight gain or weight loss as you’ve described will affect the size
of your breasts.  Breast size can
fluctuate with hormonal changes, weight gain or weight loss.  Should you lose weight your breasts will
become smaller but may not be as small or have the shape they once had.  I would suggest reaching your goal weight before
deciding on any surgical procedure.  You
may need a reduction or even a breast lift depending on the amount of weight
you lose.  Be sure to consult with a
Board Certified surgeon to discuss your surgical options in detail.

It is likely that your breasts would become smaller if you lost weight as they were smaller when you did not weight as much.

Your breast size will get smaller if you lose the amount of weight you are describing. I would wait on any breast surgery until you have lost the weight and are stable at your new weight. You may need just skin removed or some breast tissue. Only time will tell.