WHY DO I FEEL TIRED ALL THE TIME?

I HAVE BEEN FEELING TIRED FATIGUED LOUSY LETHARGIC FOR ABOUT A YEAR NOW!! IVE DONE EVERY BLOOD TEST FOR TIREDNESS SYMPTOMS ETC IVE HAD CARBON MONOXIDE TESTER FITTED ETC MY DOCTOR IS EVEN GIVING UP ON ME BELIEVING IT COULD BE ALL IN MY HEAD!! ALSO THE TIREDNESS STEMS FROM MY LEGS REALLY STIFF AS SOON AS I WAKE UP JUST GOING UP THE STAIRS THE FEEL SO HEAVY!! ALSO MY PARTNER IS FEELING THE EXACT SAME AS ME?? SHE HAS HAD ALL THE TESTS DONE TOO!! I RECENTLY GOOGLED THE ILLNESS ME AS THIS IS A FATIGUE ILLNESS CAUSED BY A VIRUS OR AFTER HAVING A VIRUS SO IM THINKING WE COULDVE CAUGHT A BUG?? ANY DOCTOR OUT THERE ON ANYBODY WHO CAN HELP PLEASE??