If you are able to articulate the D sound sometimes, the problem isn't the D sound itself. It's very common for stutterers to block on their own name and other words of importance to them. Our brain then has anticipatory fear around other words beginning with that sound. A block happens \*because of\* your attempt to fight against having a repetition. Breaking eye contact is also very common. Honestly, the way to address it is to maintain eye contact and begin speaking slowly. Practice this in low-stress situations first. Try voluntary stuttering. (H-h-h-ello, how are you?)