Infectious mononucleosis?

I'm a 17 year old female and about 2 months ago I went to the doctor for a cough. I was told I had adult croup and was sent home with some cough medicine. About a month later it came back; this time, however, my doctor prescribed me with steroids and told me to continue with my cough medicine. I started feeling a little better until about 2 weeks ago when I had an ache where my spleen is when I breathed in, which I figured may just be an internal bruise from coughing so hard. I was feeling really uncomfortable at the time and of course tired, as most all high schoolers are. Last Thursday, I decided to finally just go to the doctor since my spleen wasn't feeling much better. Since this was my third time there in about 2 months, she decided to do a blood test, which led to my diagnosis of mono. She said I had a little enlargement of my spleen, as well as something with my liver. Over this whole process of me being sick, I haven't really had a fever or sore throat or anything else mono related, except for the spleen and uncomfortable feeling, which just occurred within the past 2 weeks. I have had a few friends who have had mono before, and they missed weeks of school. I guess I'm just a little confused why I'm not feeling as bad as I feel I should with this. Do you think I'm just getting over it or it's just about to start? I don't know, just curious and scared, haha. Thanks for your help!!