Dear Ms L. -- 
By the time you read this, of course, you'll have multiple other observations to go on.  But based on what you describe here...

First, for you and any other readers, a caution: you can develop an allergic reaction even after taking a medication for months.  Not common, but possible.  So you can basically never give up that potential explanation for a problem.  But by now you know if it was allergic, as that probably would have gotten steadily worse.

But there's another very common problem with Trileptal, called hyponatremia -- literally "too little sodium in the blood".  This comes about mainly because your body is not getting rid of fluid at the usual rate, rather than keeping too little sodium.  The technical term for this process is "syndrome of inappropriate ADH secretion", or SIADH.  A mild version of this is very common with Trileptal use, and occasionally it causes quite severe versions.  

Hyponatremia can cause a wide variety of symptoms.  Yours are not typical but I've seen some pretty weird things, from ankle swelling to sort of an odd, foggy feeling like there's something wrong with your thinking.  So, some of your symptoms could be from the sodium problem, and that's very easy to check for with a simple blood test. It's also easy to fix.  I'll let your doctor tell you about that part.  She might want to get the blood test first. 

Even if this is not hyponatremia that accounts for your symptoms, it could still be Trileptal.  A doc' friend of mine says: "Medications are guilty until proven innocent".  But you and your doc' probably decided together how much you were willing to tolerate side effects like these before saying "enough" and lowering the dose and looking at alternatives, right? (thinking idealistically). 

Dr. Phelps