My 9 Year Old Son Seems To Get Very Angry

My 9 year old son seems to get very angry when ever something doesn't go his way. This has always happened and will go in waves as to how many times in a week, but lately its a few times a day. I know when the allergies are bad his tantrums are worse as well as when he is sick. I have asked his doctor about it and she isn't concerned. I am, it is unhealthy for the family to be angry and have to miss out on doing things together so often. He had his adenoids removed last month and is on 2 allergy meds, I don't know how to help him level his moods.
I wil call his doctor again. thank anyway