Losing weight but neck still looks very big, my jaw/chin are very weak. What can I do to get a better appearance? (Photo)

I'm not sure what needs to be done for my chin/jaw. I'm 19 and was very over weight until a couple years ago when I started losing weight, now I weight 82kg at 5'11 and I still have a massive neck and I think it may be because of my weak chin/jaw. I tend to find it a lot easier to breathe through my mouth, I have to force myself to breathe through my nose every day but can't do it when sleeping, thus I snore quite loud and get bad sleep. Any help would be greatly appreciated, thank you.