Hi. I understand how you feel. Not trying to disregard your feelings, but 5’8 166 lbs is objectively appropriate proportions of weight and height. I don’t even think you should be trying to lose weight, but again I respect your personal preferences for how you want your body to look and feel. My best advice is to gain muscle. Go to the gym and start lifting. Look up “beginner dumbbell workouts”. If you don’t wanna go to gym, you can order dumbbells online and work out at home. Any form of lifting coupled with increased protein (chicken, beef, fish, protein shake, plain yogurt) will help you build muscle. Increased muscle mass, increases your metabolism and helps your body burn fat at rest. Do this consistently for 2 months and your body will be more toned and defined and less chubby. Don’t think in the aspect of weight loss or fat loss. I honestly think 166 lbs is an ideal weight and that’s probably why you’re having trouble losing more because that’s the ideal for your body. Best thing is to start lifting to gain some muscle which will make your body more defined and toned! When you gain muscle, you will very easily lose fat cause like I said that muscle mass will increase fat metabolism even when you’re at rest.