This is in no way a diagnosis, but people who are new to something and self diagnose on the internet, almost always end up worrying about some catastrophic illness that they don't have.
Pick your snake up 8 inches from the end of his tail and hold him up. He should hang there for a few seconds, then try to lift his head and body back up to your hand to get a more stable platform. If he can do that without issue, his muscles and his grip are probably fine.