What Are The Side Effects Of Amoxicillin?

Hi, I have recetly been to the detist and he has prescribed me with 7 days of amoxilyn (penacilin) but every other day late into the evening after i have eaten i am still getting a bad ache in my gum on the right hand side and an earache that follows on my right ear , it so painful that i take 400mg of ibroprufenand that works but what could it be?