What can I do for weak chin/jaw & the slope from chin to my neck? (Photos)

Hello! I’m a 24/F at 5’ 11”, about 128lbs. I would say I’m fairly active, my body fat is about 16%. I’ve always had a smaller chin. But I would really like to have a more pronounced jawline and I don’t know how to fix my chin/neck. If I look down I have no chin, and when I walk I look like a turtle from the side. What procedure should I look into? Is my posture the issue? Do I have too much fat under my chin? Any info would be useful!