If you are having new swelling nearly a month after your breast augmentation, I would suggest you follow-up in person with your Plastic Surgeon. It may be fluid - a seroma - or it could be a delayed hematoma - or blood. If there is fluid in the pocket, then this can affect your implants, and can hasten potential capsular contracture, or even become infected. Follow-up with your Plastic Surgeon for an person examination. Depending, this can either be drained in the office - or you may need to go back to the OR to have it formally washed out (your incision would be partially opened, and the pocket drained and irrigated. Regardless, I would suggest following up this week if able. Best of luck!