Have you ever gone through speech therapy? If not you should seek it out. Helped me a ton. The first thing you learn is the mechanics of how speech works. You need air moving over your vocal folds to produce speech. When you block no air is moving. IMO blocks are the easiest part of stuttering to get rid of. It takes practice but if you make sure to start every word on an exhale, the chances of you blocking reduce dramatically. And if you learn to always be conscious of your breathing you can pretty much eliminate blocks.