Hey bro, I'm the exact same age as you and yes I go through the same shit. My name is Darragh but most people know me as John, James or whatever fucking J name pops out in that moment of introduction. It's tough. Theres no denying that. I also work in construction, surrounded by big egos and small minded-ness. What I have found is that most people don't care that you stutter and the ones that do aren't worth caring about. You need to start wearing your stutter as a badge of honour. Do some slow and deep breathing every morning preferably after you have had a run. This will loosen up your diaghphram and make you feel more relaxed heading into the day. There's heap of YouTube vids you can use. You will have bad days man and this sounds like one of them. You will be ok. Dont let this get the better of you. If you ever need a chat privaty dont be afraid to hmu . All the best.