Why is one side of my belly bigger? (Photo)

Sound like you have some retained fluid (seroma) or swelling + a seroma.  Repeated aspirations or placement of a drain will help in almost all cases.  Rarely, surgery is needed for this.  

Dear Jencash25,every patient is a different story and heals differently. It is hard to tell for sure without an examination. I would suggest you to consult your plastic surgeon. Only after a thorough examination you will get more information and recommendations.Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

Fluid buildup (seroma) after a tummy tuck is often talked about like it's unusual, but in reality it's a completely normal healing response of the body. Seroma is also not bad in and of itself—it's only that the risk of the seroma becoming infected is a concern. As long as you continue practicing the post-op drain instructions provided by your surgeon, this should resolve with time.

Thanks for reaching out and sharing photos. As mentioned in a previous answer, every patient heals differently. I have had patient get their drain removed and need to have excess fluid removed multiple times, and some have no issues at all. The good news is that your surgeon is on top of it and you seem to be in good hands. Keep up with the follow ups until your concerns are at ease. best of luck! Dr. Kachenmeister

There can be several reasons why you are experiencing recurrent seromas, this fluid accumulation. Without knowing anything about your medical history, course, drain usage and time in, etc. a more specific answer is impossible to provide. However, when managed appropriately and aggressively, these will ultimately resolve and the swelling abate. Any questions that you have regarding this you should ask of your surgeon who knows you and your history.Steven Turkeltaub, MD