There is something known as 'chronic EBV'-- a chronic infection with the virus that causes mono, that can cause fatigue and body aches and pains. Please check out a forum for infectious diseases; there are nuances to the testing that are beyond my experience. Another thing to consider, if you haven't already, is lyme disease.
SEE ABOUT HAVEING YOUR THYROID CHECKED ... I ALSO HAD MONO ,, MANY YEARS AGO... I KNOW WHAT YOU WENT THROUGH... ... BUT THE THYROID CAN AFFECT YOUR HORMONES,,IT IS A HORMONE ,, MAKE YOU FEEL UP OR DOWN ,,. I HAVE HYPOTHYROID.. WHICH MAKES YOU FEEL TIRED ALOT ,,, ETC ETC ...BODY PAIN- MOODY,,,SO GOOD LUCK ,,, ASK FOR A THYROID BLOOD CHECK .. IHAVE IT DONE EVERY 3 MONTHS .. AND I TAKE SYNTHROID... ... GOD LOVES YOU WE DO TOO