Want to shape up

[fitfifty]

Hi I am early 50 year old and have lost about 15 kilos and now am a quite healthy 89-90 kilos. I have maintained for about 3 years now. I had a personal trainer for 12 months but now doing it on own. I love to work out with mostly cardio, say 3 - 4 times and like doing stair running with weights, stepper, cross trainer and rower. i also do 1 alternate sprint session each week, and on cardio nearly always do about 30 minutes of HIT. I also do 2 weights sessions but dont really want want to keep increasing the weight each week but rather just to steadily improve shape and slowly lose weight. I try to vary and do different days for legs, chest/back and arms. I have a very clean diet but have stabilised for about 6 months now and this gets me down a little. I am really increasing heart rate in the cardio but still not losing ! I know is more difficult after 50, but think I would look great if I lost just 5 more kilos.. Can I please have any advice, I am sure there must be some magic ingredient I am missing ?