Brave to post your challenge, but actually stuttering as a fluency disorder is not characterized as stereotypical only stuttering initial consonants. Your stuttering is quite normal and typical. There are different types of stuttering, under different conditions, situations, and context whether it be environmental or emotional. I've had clients who have several types of stuttering. What you call a "mental block" is actually called a "block" in the profession; a symptom of stuttering, and what you call stereotypical stuttering is called "prolongations". I would recommend doing some google search into the the stuttering foundation, or look on the ASHA website and search fluency disorders. You'll find that your symptoms of stuttering are very familiar to speech therapist. Lastly, if you challenges are really impeding your life, maybe seek out a professional as i have witnessed several successful cases. GL! :)