I have been really worried for the last few months. In July, I began having extreme fatigue and muscle weakness, lack of appetite, nausea, muscle aches, stiff muscles, neck pain, side pain, and dry eyes. So naturally, I Googled. I worked myself up into multiple anxiety attacks over it until I finally got blood tests done and was diagnosed with Mononucleosis. That explained all of my symptoms, but I still have it four and a half months later and the symptoms are still bad (and I now have knee popping and stiff toes which I'm guessing may be viral arthritis, I haven't gotten it checked yet) and I'm worried that maybe the blood test showed a false positive. But the CBT should have shown anymore blood conditions or even certain autoimmune diseases, but now I'm really worried about MS cause it has some of the same symptoms as Mono and can't be seen from a blood test. I can't get an appointment for more labs until the end of the month and I'm freaking out really badly that it's even worse than Mono and I don't know how to calm down. My anxiety has skyrocketed since all of this began and I'm so scared.
i know you feel scared, but keep in mind that you can take any symptom and it can be found in 100 or more non serious conditions. ive had most of your symptoms many many times over years. all due to chronic anxiety.
If you have anxiety, it could lower your immune system and take longer to recover from mono.
It doesnt sound like MS.
Are you taking care of yourself? EAT HEALTHY, DE STRESS, DONT GOOGLE. STAY BUSY!
Your mind is overthinking and going negative. 99% of what we worry about doesnt happen.
Listen to some great meditations for overthinking, anxiety, etc on you tube. they help! 
The trouble is there are a lot of conditions that seem similar to MS, and it can be difficult to diagnose straight away. maybe look on this site for an MS discussion group . they will be able to advise you better as they will have the symptoms. I hope you get the help you’re looking for. be strong​:revolving_hearts: