It sounds like you may have venous leak - to enable an erection, blood has to flow IN to the 2 chambers - the corpora cavernosa, one on each side of the penis. But in addition, there’s a ‘veno-occlusive’ mechanism that has to shut off blood flow OUT of the penis. If that doesn’t work properly (venous leak), the blood doesn’t stay trapped in the penis & it either doesn’t become fully erect or it may become erect but it can’t be maintained for long. It’s like trying to fill up a bucket with a hole in the bottom. There’s a test called penile Doppler ultrasound, they inject medication in the penis to cause an erection (don’t freak out - it’s nearly painless), then use the ultrasound to measure both inflow & outflow of blood. This might be helpful in determining the cause of your prblm.
Also you mentioned hormone levels - did your test show a low level of Testosterone? It does sound like it, since you have trouble building & maintaining muscle. And this could be related to the erection problems - low-T can sometimes cause venous leakage. Unfortunately, the Doppler Ultrasound test I mentioned is usually not covered under most insurance plans...
Bonzodog, the man, has given you some great ideas of what to look into. Your testosterone level looks right in the middle, so not a problem. https://www.medicalnewstoday.com/articles/323085
This is the test bonzo suggests and I do to. https://radiopaedia.org/articles/erectile-dysfunction?lang=us As he mentioned, it is painless, not hard to do. Your insurance is US based? It doesn't cover urologists? It should. that's a medical condition. Impotence is a problem. Talk to your doctor about how to code it to be covered under your medical. But that diagnostic test should be done to tell you what may be the underlying cause so you can treat it.