I have blocks as well where I’ll be completely fluent for a period of time and then it comes back. I push through it and eventually it goes away again. I do the same thing, where I’ll switch the word I’m thinking of saying if I know I’ll have a block. When I drink alcohol, I have no stutter either. I know it’s something psychological. I noticed it happens more when I’m under a lot of pressure or going through a major like change. Sometimes it’s random. I’m a 42 year old woman. I’ve never been on medication or brought it up to a doctor before. I wish there was a way I could overcome it though. I feel your pain and hope we can at some point fully overcome it permanently.