A Hi there. Great question.
Based on your photographs and complaints of difficulty exercising and discomfort (feeling heavy), I think you would benefit from a breast reduction
The main difference is that a breast reduction include removal of breast tissue, while a breast lift is just removal of skin. Both procedures will reshape your breasts and raise your areola and nipple up to a more youthful position.
Please see a board-certified plastic surgeon in consultation to be evaluated and learn more about your options.