Thank you for your question.
I'm sorry to hear that you've been having problems after your abdominoplasty. While recurring seromas are rare, they do happen from time to time.
At this point, you have a few options for management. One option is to continue needle aspirations to see if it will resolve. Ultimately, however, this is unlikely to prevent further seroma formation. Typically, if your seroma returns after multiple attempts at drainage, a more aggressive option is warranted.
Another option would be placement of a drain, which could be a passive drain (such as a Penrose drain) or a suction drain (such as a Blake or Jackson-Pratt drain). The advantage of the Penrose drain is that it's a simple, in-office procedure that doesn't require anything other than local anesthesia and some antiseptic. A small incision is made into the seroma pocket, and the drain is placed. The disadvantage is that while the drain allows the fluid do escape, it doesn't actively try to close the pocket - it relies on the body to try to get the pocket closed.
With the suction drain, the primary advantage is that it simultaneously evacuates the fluid and applies negative pressure to try to get the pocket to heal faster. The primary disadvantage is that placing it can be more involved, and in some cases, requires sedation or image guidance, though not always.
Another option is to try a sclerosing agent, such as doxycycline, a common antibiotic. This can be done at the same time as a needle aspiration. During this procedure, the fluid can be drained through the needle, and afterwards, while the needle is still in place, the doxycycline can be injected into the pocket. The sclerosing agent then scleroses (scars) the tissue shut, thus preventing recurrence of the seroma. The effect isn't instantaneous, but typically will be effective within a few days. This will sometimes need to be repeated.
Ultimately, your surgeon knows you best - I would suggest that you should express your concerns to your surgeon and make sure your questions get answered. Additionally, you're always entitled to a second opinion - if you're not satisfied with the answers you're getting, then get another perspective.
Best wishes.