A sudden change is bad. I would expect your libido to drop over the years, but you said it crashed over the past few months and that sudden drop is indicative of something being wrong. Like SilverNeurotic said, a second opinion could be what's needed. Maybe prostate problems or testosterone levels or who knows? But that sudden change needs checked thoroughly.

Being listless, tired and no libido though really sounds like a testosterone issue to me. Mine is normal (for a 42 year old man), but I'm still tired and listless. I was able to afford taking Nugenix for a month and felt like a million bucks so maybe something like that will help as well for you?