You noticed that inhaling makes it worse. I used to do that, too. During a block there is a panic sensation aka fight or flight response. Your diaphragm tightens and you take a shallow, quick breath. That inhale adds pressure on larynx, lips, tongue (depending on the sound). The inhale fuels the block. It is counter intuitive but you want to say the word in unison with an exhale. Keep eye contact with the listener. Inhaling as you say the word strips the energy from the stutter. If anyone thinks you have to inhale, then relax, then start the word, that is false. To prove it place your hand on your chest and count out loud to 5 without taking any breath. That is FIVE words without a breath. Good luck.