If you've got myriad problems it doesn't mean you should call a myriad exterminator, it means you've got countless problems; loads of them; too many to count. Welcome to the club.
Myriad is one of those words rarely used in speech but only in written form. You would usually use a phrase like "lots of" or "loads of" instead. I mean, you could say "I've got myriad problems," but everyone would probably just laugh at you, and rightly so. This word derives from ancient Latin and Greek words meaning "ten thousand."