3 weeks post-op and I woke up with a my right side red, tender, and warm to touch. (Photos)

Thank you for your question.  From your history it is possible that you have developed an infection on that side.  This is unusual 3 weeks out but can certainly happen.  Any new onset of spreading redness should be reviewed by your plastic surgeon ASAP.  If unavailable then your family doctor or the local emergency department would be alternatives.  It sounds like you have already done that and your PS has put you on antibiotics.  They will want to follow this closely with you to make sure it is getting better.

Dear jamie0913,I understand your concern. Based on your symptoms, you might have an infection.  However, without a proper assessment it would be difficult to determine what is wrong. It is best that you visit your plastic surgeon for further assessment. Only after thorough examination you can get proper recommendations and advice.Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Your photo shows redness that is suggestive of cellulitis, a skin infection that can occur around an incision. Your surgeon should be examining you every couple of days and if the oral antibiotics do not help, you may require one or more of the following:1. IV antibiotics;2. Aspiration and/or placement of a new drain to remove any fluid that might be accumulating under the incision in the deeper space between the fat plane and the muscle;3. Opening of a portion of the incision to drain the wound if there is pus.With proper followup care, infections of tummy tuck incisions are usually straightforward to manage with little long term impact on the final aesthetic result. Make absolutely sure you are following up closely with your surgeon! None of the physicians here can direct you formally as we have not examined you so you need to followup with the surgeon in person.