Bad allergies with mucus in back of my throat?

[Angela]

ok, I have been using Clariton for over a year, and I'm pretty sure the medication doesn't help anymore cause my bodys used to it. I live next to the beach so there's always fog and my parents say it allergies, because I have trouble breathing sometimes and I always have mucus in the back of my throat. But, when I went into the desert, where my parents say "there's nothing to be allergic to" it gets really bad....also, another strange thing is the jumps in my temperature. As in, (and I make sure not to eat or drink anything for a few hours before I check my temp.) it gets to Be around 103 degrees F. and then about 25 minutes later drop around the low 90's. But, my friend said it was completely normal. So, are there any other medications that will help clear the mucus and help even my breath? Or should I just go off Clariton for a little while? It's not like I'm fat or anything, but it's hard to do the mile w/o Clariton (it still helps a little) and my P.E. teacher wont let me sit out
I'm 14, and no matter where I am my allergies act up