Deoxycholic acid or liposuction? (Photo)

Since you were slim and have very little subcutaneous fat what makes you think that you have fat to remove in your submental area?
I think you’re referring to the bellies of the digastric muscles.
Injecting fat dissolving chemicals into your muscles it’s probably going to be uncomfortable and not give you what you’re looking for. That is simply your normal anatomy.
You have no fat to remove and any attempt at doing that will probably leave you looking like somebody tried to do cosmetic surgery on someone who shouldn’t have it.
Consider a moment of gratitude and reflection for those who do not have a visible Jawline.
If you continue consulting somebody is likely to offer you something because you asked for it.
Don’t rely on people trying to make a living doing aesthetic treatments to serve your needs first.
You do not need fat removal.
Your facial anatomy is excellent and there is nothing incorrect about it. It is normal.
Best,
Mats Hagstrom MD