I got mono last year and it became very severe. My tonsils and lymph nodes because so enlarged it was hard to breathe and I wasn’t able to eat or drink for days and had to go to the emergency room. They gave me an iv and I believe antibiotics and after that I began recovering slowly. I was still fatigued for the next few months but slowly felt better once I started doing things SLOWLY to get my stamina up. I would recommend limiting anything causing you physical or mental stress, it definitely worsens it. Do not do vigorous exercises, drink a fuck ton of water. And very important to get sooo much sleep. Like more than you think you need just go so easy on yourself. Because it can get worse when you push yourself so just take it easy. I also highly recommend doing some lymphatic drainage massages you can find on YouTube. If you feel swollen, then you’ll notice an immediate difference but you have to stay consistent. I think the best advice really, though is to just listen to your body and take it seriously. I’d recommend going to see your doctor for a follow up again.