Do I need a breast lift at 20 when I haven't had kids yet? (Photos)

There seem to be two issues with your case:  size and shape.  The size reduction and shape reduction can be achieved with a breast reduction surgery.  I would look at techniques that stand up to the effects of gravity and time.  Take some time from your work out schedule!  I think at your age you will have great long term outcomes and affects on your life!  Best Wishes!!

A breast lift would enhance your breasts. The milk of pregnancy could change your surgical results. After pregnancy, your breasts could remain the same size, slightly bigger, slightly smaller and/or droopier. And, what can happen, can change from pregnancy to pregnancy. I recommend an in person evaluation by a plastic surgeon to be measured and discuss your goals. After I measure and discuss goals with my patients, we then look at pictures of former patients with similar measurements. My patients tell me that this process is very helpful in determining what size breast implant is right for them. 
Dr. Ted Eisenberg, Board Certified Plastic Surgeon and Author                         
RealSelf Distinguished Hall of Fame Inductee
 

Hi, thank you for your question. 
Based on your photos, your breasts appear to be very large and droopy. If you feel that they are too heavy for your back, you may benefit from a breast reduction. If you like the size, but want them to be perky, you are a great candidate for a breast lift. Both procedures will help restore the breasts to their natural position with a "perky" appearance.
Consult with a board certified plastic surgeon who can answer your questions and go over your options in person. 
I hope this helps. Best of luck!