There is an elite group of CW operators that struggled with H vs S vs 5. We call ourselves "all of us", and we meet weekly at Arby's!!! Keep practicing, and eventually you well pick the sound out based on the context of the word. I've only been at it less than a year, and I still struggle with this combo more than any other characters. I also strongly recommend not writing things down, practice head copy. Keep your speed close to 20, and keep pushing the farnsworth speed up when you start to get comfortable. You're not going to grow if you don't push yourself. If you spend 30 minutes a day practicing I recommend 5 of that be practicing head copy at a higher speed. Just relax and listen, and don't worry about getting every character right. Once you start hearing the characters faster it's more relaxing at your normal speed.