I have had mono for about a month now, and the symptoms have all come and gone except for the fact that the past two days now I have experienced some chest tightness, I m not sure, maybe it s in my head, but I just feel like breathing isn t as easy as it should be. My back is also sore, I know it s got to be muscle related, but I haven t done anything to make them sore, my heart rate is normal as well. I m just worried because I recently had a friend who died of myocarditis and now this kinda of stuff is freaking me out, I m only 17 so of course I would like to remain alive. I m really just wondering if I should go right to the ER or what? I ve asked my parents and all my friends and relatives what I should do and they all say it s probably just from the mono. So I would really appreciate an explanation from a doctor in what it could be, thanks