Eighteen pounds is difficult because you're so close to your goal weight. The difference between your current weight and your goal weight might be a mere 100 calories per day.
For some, especially if they arrive here with serious health problems or 100+ pounds overweight, just decreasing the amount of carbs they eat by ditching grains drastically reduces the number of calories they eat and so in the beginning, it seems as if they're losing weight effortlessly.
You're ahead of the game in that you remember hitting your goal weight as an adult, and remember what you were doing when you were there. If you can replicate that in the context of Primal, you'll be there in a few months to half a year.
Nuts are incredibly fat and calorie dense - pretty much second to pure fats like butter, olive oil, coconut oil, etc. I'm not sure that they should be a part of a weight loss protocol. Also, they have the disadvantage of being a snack type of food. It's just too easy to go for a few and then eat 500 calories worth. A quarter cup of nuts can have between 150 and 180 calories, the same as 4-5 oz of 95/5 ground beef. I see nuts as more of an issue than fruit. (But that's just me - what works for me may not work for you.)
Primal is good. But losing weight is tough. And losing the last 20 pounds can be the toughest. Hang in there, eat healthy/primal, and keep the faith. You'll get there.