I’m getting some bad vibes from these comments. I do agree though, they could of just not been blunt about it. Try not to use your dads stutter as an example because no one knows if the same thing will happen to you. However, it is good to have a goal in mind (to be fluent) but don’t let it get you down when you feel like you’re not achieving it. I’ve had the same situations with a lot of letters, my current ones are TH, F, S and A. I guess all of them can be challenging depending on the circumstances. My advice is to stop caring so much and just let it happen. I know it sounds counterproductive but you’ll only see results once you’ve regained confidence by accepting and embracing your stutter. Deep breaths can also help. When you’ve started stuttering or feel the block coming, stop, breathe and then try again