I've been interested in the strength world for a long time. While I don't limit myself to any specific muscle groups, I never gain much strength. And when I do gain strength, I tend to lose it very quickly, even despite continuation and progression. In other words I will get a tiny burst of strength increase some days, but it fades away and I go back to "neutral" very soon (few days). I also have no balance of strength, as some days I'll feel much stronger and energetic in lifts, and other days I'll fatigue from almost nothing.
Factors that could be considered:
1.I breathe through my mouth, not nose; very little breathing through nose. For this reason I don't breathe much, meaning I have adapted myself to breathe less to avoid gaping like a fish for breath out of my mouth, which looks stupid. Also, I have been made fun of for doing it, so I've learned to do it much less often, and in smaller amounts, etc.
2.I have no endurance and never train for it. Since I don't have any goals in the fitness world, it is pointless to me to consider doing reps since my only goals are strength, power, and ability to apply large loads of force. Fitness isn't crucial, but I don't know how "not important" it may be in the long run, since I see hugely fat and obese, out of shape, lazy people that can lift 600 lbs.
Often I'll slowly try to increase the weight over every week or so, but I'll just do a few reps. If I lower the weight I do too much sarcoplasmic training, which I don't care for and doesn't show strength results. If I "moderate' the weight I just fatigue moderately, but don't see long-term gains. I've tried mixing the exercises around, changing types of weight, angles, doing bodyweight exercises, etc. There's no real improvement no matter what I do. I see people lift a weight twice a week and they're gaining strength instantly, and I do it for months and there's no noticeable progression.
I eat what I can, but roughly 2,000+ calories a day at 5'9" tall. Probably 60-100 grams of protein, decent nutrients, but diet could improve if I had the option to improve it. I get 6-8 hours of decent sleep every night; sleep isn't great, but it's decent. I do static/dynamic stretching, warm-ups, have normal levels of testosterone, start with light weights to get a good "feel", then work up. What could be wrong here? I was advised to consult a physician by some people, but it sounds kind of stupid since there's no noticeable problems with me that would impede strength gains.
Programs? I don't follow any, but any decent regimen of training should increase strength. People got stronger before "strength programs" existed, so I will not consider any, including Starting Strength.