Alert your operating surgeon about your condition. They need to evaluate you and treat you asap. It appears you have wound separation, tissue loss with delayed healing and infection despite your being on antibiotics. You need to be seen and treated by your surgeon.
Is this infected?
Yes, you have a small postop infection at the junction of incision lines following your breast reduction surgery. This can often be managed without additional surgery by a combination of antibiotics and topical wound care. Talk to your surgeon right away.
You know a wound is infected when it is painful, red, hot, and you have fevers or chills. Let your surgeon know your concerns.