I a man currently going through something similar to your son. I was misdiagnosed with fibromyalgia for almost 10 years. I started feeling weaker and my pain became debilitating worse than it ever has, lost my career because of it and couldn’t walk 5/7 days for 3 months. I had my pcp run the full work up, my gut said there’s something wrong. I ended up having degenerative discs disease which ended up after 10 years now it was only manageable and not treatable which my pain management oversees… within the next 3 months I had mono. I had it once when I was 14, then two months later and about 40 lb weight loss without trying they finally did more bloodwork. I started getting weaker naturally and then my blood work came back and I now had astronomical EBV levels and my positive ANA were back. I was diagnosed with CAEBV. I was down from 188 to 133 from May to December. My family thought I was doing drugs and my wife and her family who we live with were now scared worried. From January to now I have had lymphadenopathy over 5x, fevers that lasted over 6 days, swollen organs, on a 3500 daily calorie diet and about 4 weeks ago I was bit by a tick at work. Within a week I couldn’t move my arm because it was numb but hurt so bad, it felt like there was so much painful pressure in the back of my head, list can go on. They put me on Doxycycline which made my body have astronomical ACID levels and I was taken off only after 2 weeks instead of the 4. Within 3 days I had such a bad rash on my chest, arms, back and face that my wife could see it in the pitch black, fevers, my pain is back to all time high, All my lymes tests have come back negative, my ANA is positive but so low that they don’t do anything for it apparently, I literally feel like weights are on my body, and the headaches are horrible. in some ways I am in the same boat as your son. At 27 this isn’t the life anyone should live.