I am 11 weeks out from 2nd Kybella treatment. There is still a fat, mushy blob under my chin, worse than baseline. What now?

It takes a series of treatments to get good results with Kybella. Keep in mind, Kybella is good for dissolving the submental fat under the chin area while contouring the jawline and making the chin more defined, but a combination approach is needed to get the most improvement with non-invasive options. I recommend a combination approach with Thermage, Ultherapy, and Exilis.
VASER Neck Liposuction in combination with ThermiRF, Renuvion (J-Plasma) and InMode FaceTite is the best alternative for contouring and tightening the chin area. I recommend getting a formal evaluation with a cosmetic dermatologist. Best, Dr. Emer

Without pictures can’t tell you how many you need but in general my experience has been that most people who have submental fat will need 3 to 4 treatments.

Some people may do better to wait longer times between injections, since the body can take 3-5 months for final results to be seen after even a single injection session with deoxycholate (the active ingredient of Kybella).  It is a judgment call on the part of your doctor as to the timing of a subsequent injection session.  
The "mushy" feeling is dead fat that has not yet solidified into nodules.  The nodules then are slowly broken up and ingested by macrophages of your immune system before the dead fat is eliminated from your body.  
As someone who has injected fortified deoxycholate (42mg/ml instead of Kybella's 10mg/ml concentration) for more than 12 years, most of my patients have only needed 1-2 sessions to get the results they were very happy with....so you may likely need more sessions than 2 with Kybella to get there.  Nevertheless, I am confident you will eventually get there.  You will need to be patient, as a large part of this process depends on your own body's immune system to break up and carry away that fat killed by the deoxycholate. Once you form nodules, massage, warm moist compresses, and 1,3-D-Linked Beta Glucan (BetaForce is a great brand out of Columbia, SC) can help to rid you of nodules faster.
I hope that helps you!