First, annie get your gun! :)
Second, I never had mono (I'm a 22 male), but I have had the symptoms that you are talking about. I am a big believer in "ruts". I have had highs and I have had lows and I am currently coming out of a low. (I had severe tonsillitis and was bedridden for 3 weeks) I am a runner and being sick obviously severely impeded my workouts. After my sickness was over I dealt with crushing anxiety, fatigue, nausea, shortness of breath, lack of appetite and feeling like I was going to faint. (i have a really long history with anxiety) I don't take meds for it because I was self medicating with running. After my sickness I wasn't able to exercise and I was so scared of losing that that it brought my anxiety bank 10 fold. A few days ago I was finally able to do a small amount of exercise without any shortness of breath and now 2 days later I feel like my old self. I can't run as far as I could because i've lost some fitness but I am definitely back on the right path.
That being said, mono is something that will be in your system your entire life but i've personally never heard of it coming back and being as debilitating as it is the first time around. I believe less in medicine and MORE in DOING. Do something that makes you smile, no matter how small or how little amount of time it takes up, just something and then build on it. You sound like you're in a "rut" and you just need the right catalyst to get going!
You should also explain these symptoms to your doctor, it is always incredibly reassuring to have a clean bill of health. Your symptoms could be cleared by a simple blood test! The worsening of health everyday is because you didn't do anything good for yourself the day before. Fatigue begets fatigue, eating poorly leads to eating even more poorly. It's a vicious cycle that you CAN break!
Hope everything turns out better for you soon!!
Thank you that was a lot of help, and I'm glad to hear you're running again. depression ive been told could also lead to anxiety or something along that and my mom suffers from it as well. but ill definitively give your advice a shot and tell you how it goes :)