Maybe you should try creatine.
Athletes use it to boost muscular development, it's produced naturally in the body, and its use seems to have relatively few side effects.
Here is a paragraph from a Wikipedia article on the health effects of using creatine:
Current studies indicate that short-term creatine supplementation in healthy individuals is safe, although those with
renal disease should avoid it due to possible risks of renal dysfunction, and before using it healthy users should bear these possible risks in mind. Small-scale, longer-term studies have been done and seem to demonstrate its safety. There have been reports of
muscle cramping with the use of creatine, though a study showed no reports of muscle cramping in subjects taking creatine on a 15-item panel of qualitative urine markers. Creatine did not cause any clinically significant changes in serum metabolic markers, muscle and liver enzyme efflux, serum electrolytes, blood lipid profiles, red and white whole blood cell hematology, or quantitative and qualitative urinary markers of renal function.
Apparently, it can worsen symptoms if you have asthma.
It won't enhance muscular development like a steroid regimen would, but it is far cheaper, far safer, and legal to use.
It's sold over the counter.