Why am I not in stage 5 on tanner scale like I should be?

If you are on birth control then you clearly have seen an Ob-Gyn. I would let your Gyn evaluate your breast development and counsel you. Also, be aware that there is a huge variation in what constitutes a 'normal' breast. It appears you are in nursing school, when you start your clinicals you will appreciate how different people's bodies truly are.

Thanks for your question. It is, however, better asked of your gynecologist or an endocrinologist who deals with the Tanner scale more frequently.That said, at age 20 it is rather unlikely that further breast development will occur. Any change in breast appearance would require surgery, most commonly with implants, occasionally with fat grafting. A consultation with a plastic surgeon will provide you with information regarding your options. All the best. 

At age 20, you most likely will not have an increase in breast development unless you gain weight. However, a consultation with your gyn doctor would be helpful. You may be a candidate for a breast augmentation. Just for full disclosure, a breast augmentation in my NJ practice costs $4100 plus the cost of the implants. Saline $1000 additonal. You need to be 21 years of age for silicone implants. The fee includes the Board Certified Professional fee, B/C anesthesia fee, and the Medicare approved surgicenter fee. This is an outpatient procedure that takes about one hour to perform.Best wishes