Mystery Illness Stressing Me Out

My oldest daughter Elizabeth has been suffering almost two months from a mystery illness that is causing her to miss school more than all of us would like.  She has had nausea, vomiting, fatigue and weight loss, almost 20 pounds, since March.  She seems to have trouble keeping food down increasingly and now has chest pain.  Her pediatrician hasn't been able to figure it out, so now we are going to a gastroenterologist and we were able to get an appointment on Wednesday.  She has her last AP exam coming up this week, prom in two weeks, and of course graduation next month.  I know it isn't bulimia because she feels horrible most of the time now, not just throwing up.  We bought her prom dress last week and now we may have to have it altered so it doesn't fall off of her.  We are hoping for answers very soon so she can enjoy the end of high school and go off to college without problems.  I am struggling with a lot of anxiety over this and many other things today.  "Breathe!"  I keep reminding myself.  I can't wait til the end of school for everyone.  And Caroline was acting very manic again yesterday, so we are back to the doc tomorrow.  She will miss her classes again today which is stressing me out as well since these classes only go to the end of May.  Lord, give me peace!