Enlarged Lymph node above clavicle

My 8 year old daughter was complaining of her throat and neck hurting.  I could feel her lymph nodes were enlarged so I took her to the doc. A LITTLE HISTORY: In Sept of 2007 we had quite a scare...The left side of her face, neck and throat swelled up, she had a fever that stayed around 100.5 and her lymph nodes were huge.   She tested positive for Mono...I thought she was a little young for Mono...but her face was still swollen.  Her bloodwork came back abnormal and we were 2 days away from her appointment with a Ped. Onc.Hemo.specialist...when she went to the dentist and we discovered she had 2 severely infected teeth.  Once they were removed, the swelling went down and fever went away and bloodwork was normal.  PRESENT: The doc said her throat looked ok but her lymph nodes were enlarged in her neck and above her collar bone on the left side.  I'm freaking out because after research from the previous incident, I know this is the last place you want the lymph nodes to be enlarged.  I'm waiting for an appointment to be set up with the Ped Onc Hemo guy again but I'm not very patient.  What, besides cancer could be causing swelling in this area??  She has no fever, the nodes are very tender.  The nodes in her neck, above clavicle and in groin are enlarged.  I thought weight was ok but at the doc she weighed 48.9 (Monday) and last night she weighed 45 (Tuesday).  I know the scales may be different but either way, I'm pretty sure she's lost weight.  Could the mono be back??  Any help would be greatly appreciated!