Omnicef and tired and sleepy

my 2.5 year old son began taking Omnicef after 2 rounds of amoxicillan did not work for a sinus infection. His prescription is for 14 days. By day 6 he would not nap but was constantly tired. By day 9 he began to sleep more, sleep later, go to bed earlier and take longer naps. He started to be antisocial and cried constantly. By day 10 he was throwing fits, throwing toys, crying and screaming about everything. He was even beginning to be hurtful by saying "I don't love you anymore." This was all out of the ordinary. Even when he was sick and not feeling well, he did not act this way. Just clingy to his parents. I gave him the last dose last night before bed and today has been the worst day ever. I have never seen him act so out of control and disobedient. At first we thought he was just tired and sleepy. But now that we have read these reports, we truly believe it is the omnicef. We will see our Dr. again tomorrow and tell him about the side affects. We won't be using this drug again.