My four year old son was put on Singulair about a month and a hal...

My four year old son was put on Singulair about a month and a half ago for allergies/very light asthma. I was told that it would help him to possibly outgrow those conditions, and that we would re-evaluate in six months. At first I wasn't very consistent with giving it to him, but for the last two weeks or so he has had it every night before bed. For the last week he has not been himself. Whining a lot, upset about very little things, much more aggressive towards his sister, hitting, kicking, throwing fits. Twice this week his day care center staff pulled me aside and said he has been acting horribly. Upset about little things, angry, kicking, not listening, being very defiant...in short not acting like himself. Same as what we are seeing at home. It's like his behavior has regressed back to a two year old or worse. I made an appointment for him today because of these behavior problems, plus he seems to be suffering a possible ear infection and bronchitis again anyway, which is what we started on the meds for in the first place. A co-worker remembered that we had recently started medication, and inquired about whether or not I thought that could be causing the behavioral issues. I did a search on google and came to this site. Reading these stories is like a light bulb switched on in my head! I feel horrible, why didn't I think to ask about side effects, why didn't I think about the meds being a possible cause of his behavior? No matter what the doctor says today, I am taking him off the Singular immediately. I will be in search of natural remedies to treat his allergies.