20 days post op tummy tuck and my lower abdomen feels a little softer like a water balloon.

Niki,It sounds like you have developed a postoperative seroma (fluid collection).  They need to be drained so I would call your surgeon's office and ask who is covering for them while they are not available.  The seroma (if it is one) may be drained in the office with local anesthesia.Best of luckDr T

based on the description it sounds like you may have developed a post- operative fluid collection or seroma. Wearing your support garment will help to try to resorb the fluid but in the end you may need to have it aspirated. Otherwise this seroma fluid create a permanent cavity that may be more difficult to treat. I also worry about these fluid collections getting infected. Iwould recommend you seek out another surgeon to address this as soon as possible. Hope this helps. Good luck.

based on your symptoms it is possible that you have what is called a Seroma;which is a fluid collection under the skin flap. However you need to be examined to be sure. 

Although your surgeon is out of town, there should be a covering physician. Please contact their office to be advised of how to proceed.

Best wishes!