You have a nice face shape to start with. :)
If you wish to enhance your features and achieve a slimmer face with more defined jawline, I would suggest you to try the following treatments:
1) Chin Filler
Dermal filler can be injected into the chin to achieve well-defined chin and more V-shaped looking face. Your face can look slimmer when your features are sharper.
2) Botox Jaw Reduction
Botox jaw reduction is another popular treatment used to shrink jaw muscles so that the face will look slimmer and less square. This treatment is suitable for you if you have muscles that is bulging when you clench your jaw.
3) Exilis Ultra or Venus Legacy - Face Slimming Treatment without Needles.
You might want to consider this treatment if you are looking for a needle-less option. Radio frequency is used to stimulate collagen production, lift the face, and slim the treated area.
It's advisable to have a consultation with an aesthetic doctor to assess your condition and discuss about the best treatment for you.
Hope the info above helps!