Regarding lifting weights and stretching...the verdicts on this are all across the board. Part of how I got into tailoring is my own personal history with weight lifting, fitness, etc and how it affects the body. I actually have pitched and sloped shoulders as well but with a muscular build. I tried different things forever to get my shoulders to retract and not slope so much but the older you get the harder it is. If you're not a weightlifter normally, posture is affected by primarily genetics and your normal day to day movements. People that have pitched shoulders and a stooped neck by genetics really have it tough when they're sitting at a desk or doing something that makes the body bend over too frequently. Especially if you're tall.
If you are a weightlifter, doing too many bench presses and lat pulldowns...you know the 'ahnold' moves? That'll take your posture in the direction of pitched and stooped because it tightens your chest pulling those shoulders forward and the lats and rotator cuff are actually fully responsible for forward shoulder rotation...not the chest. Combine that with endless sitting as Americans are more prone to than standing and your rhomboid muscles will start to weaken and lengthen as well. There arent' many exercises that strengthen and tighten those rhomboids which are primarily responsible for shoulder retraction. There is one, however, which you can try in conjunction with stretching your chest and front shoulder muscles.
What you do is you buy two smaller nerf footballs. You take those footballs and you position them at the very back of your shoulder deltoid muscles while leaning against a wall. Yes, you may need help. From here you're going to contract the center of your back muscles...the rhomboids. You hold and release. Over time and repitition this will tighten them up. You use nerf footballs because they don't exert resistance outward when you contract and release so it disengages your lats. There is no rear-ward pulling exercise that specifically isolates your rhomboid muscles like this one. Every pulling exercise will engage your lats. An uninformed well-meaning person with pitched shoulders will pull with his lats til he's got a back like Ahnold only to no avail because big lats make shoulder protraction worse.
Hope this helps!
Thank you. My work tends to be pretty physical (I'm a filmmaker, so I have to lug gear around) and I've been able to work out a schedule that will let me get to the gym with an eye towards building some strength for that and, as a secondary thing, making it easier to fit into OTR clothing. I figured my lats must have been part of the issue. I may just try that exercise -- fortunately, I'm still young and malleable.