I have a "turtle" kind of neck. My jawline and chin seem to be connected which is making my jawline undefined. (Photo)

From the photograph alone in your description it sounds as though you're an excellent candidate for liposuction of the chin. Problem areas that don't respond to weight loss generally do well with liposuction. Liposuction of the chin can be done with local anesthesia only.

I treat this everyday in my practice. Properly performed energy based liposuction and physical fat removal will do fantastic to remove the fat, lift the skin, and contour the jawline. I pretreat everyone with Botox 1-2 weeks before surgery to relax the neck muscles, allowing for better retraction of the skin after surgery. Then after treatment we do skin tightening with Venus Legacy to improve the results and decrease the neck swelling. I suggest you only see an expert for treatment of this area as a meticulous surgeon is required to get great results and complications in this area can be devastating both medically and cosmetically. Best, Dr. Emer. 

 Based on your photo alone, I believe a very conservative spot liposuction to your  jaw line  and jowl area should create a good improvement.  Your plastic surgeon should check for  how full your salivary glands are as well, since this cannot be improved with liposuction.  Very tight neck muscles called the platysma can create a  full appearing  chin as well . This is most easily treated  by botox.  So before you commit to liposuction, make sure  a board certified plastic surgeon evaluates you for these  anatomical considerations. Prashant Soni M.D.T