Hi
In clinical trials with Keppra adverse events such as somnolence, dizziness, depression, anxiety, emotional lability, hostility etc have been seen in patients. (http://www.rxlist.com/cgi/generic/keppra_ad.htm)
It is recommended that you should call your doctor at once if you have any new or worsening symptoms such as mood or behavior changes, depression, anxiety, or if you feel agitated, hostile, restless, hyperactive (mentally or physically), or have thoughts about suicide or hurting yourself. (http://www.drugs.com/mtm/levetiracetam.html)
You should discuss your symptoms with your doctor to find out the cause and to start treatment, as required.
Take care and do write in if you need more information.
Regards
My 13 year old daughter takes 750 mg of Keppra twice a day for Seizures. She has some irritability but other than that she does fine on the meds. It has been a lifesaver for our family.