Don't give up, you're not alone! It's a battle for all of us and it does get easier as you get older. My stutter was a lot worse in my teenage years and it was only when I started to accept it, get professional help and push myself out of my comfort zone that I got better and my fluency improved. It's good that you're aware of the letters you struggle on and you're already getting help. I would recommend pushing yourself out of your comfort zone when it comes to social interaction and speaking generally, that's where I saw the most improvement but only do it when you know you're ready. We all have good and bad days with our stutter but this community is here to listen. If you want to chat hit me up!