lean out

Hello, I am 5'4" 123lbs 21% body fat and 51 years old. I have been working with a trainer for 18 months and in general quite happy with the results that I have seen. However,he, (and I) have been trying to get my weight under 120 and body fat under 20 and I have been struggling with these numbers and being so close for the last 6 months. I will get the weight to 118 and the bf goes to 21 then I can get the bf to 19 and the weight goes up. He now has me lifting quite heavy several times a week with amino acid supplements. I do a minimum of 6-8hrs of cardio per week. What else can I do to get there? Is this the right tactic? my diet is clean and I allow myself one meal per week (Saturday night date night) to eat a meal out.