5'2, 104lbs, 18, what is considered a normal breast size for a girl of my age and weight?

Dear Oil Fox,
there is no range of normal size of breasts. Every individual has a different breast size and shape and there is a great variety. In case of any breast issues, a lot can be improved with surgical and non-surgical procedures.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

Thanks for your question. Unfortunately, there is no "normal" breast size. Every woman is completely different. If you have concerns about your breast shape or size (too big OR too small), there are resources and surgeons you can seek out. Good luck!