For years this has always been an issue, but I can't afford to see an expert anytime I wish, and information these days can be self-researched, learned, or found out online by experts who will answer questions in their free time, people with similar issues, etc.
But my problem is that I have this unstoppable tiredness, laziness with my arms/shoulders, and discomforting feeling of stretching out my arms, overhead or just straight out, and feel highly accustomed to slouching, and just letting gravity "weigh me down".
Everytime I do overhead presses with barbells I feel this sensation as if my shoulders are moving in a way they shouldn't be, usually resulting in shoulder aches, tightness, pains, tiredness, or pure mental strain to even hold my arms over my head without becoming incredibly tired/uncomfortable. It is like a stiffness, tightness, and fatigue that never goes away, and pre-stretching, post-stretching, or stretching in general doesn't relieve the issues. I had initially thought it was the result of weak shoulders, but even after endless exercises, and some minor improvements in shoulder strength, the feeling won't subside.
It's not just physical but mental, i.e. like an unwanted strain to simply hold my arms out, overhead, and feeling tightness, discomfort, strange sensation, etc.
Is this a known issue, a byproduct of weight training/strain, or some problem unrelated to exercise/lifestyle?