Has anyone given their LO amoxicillin yet?

My daughter has had a cold for going on three weeks. I took her to the Dr today and he didn't see an ear infection or anything crazy but said he was going to prescribe amoxicillin in case of a sinus infection. She has been extremely congested and unable to sleep. Has anyone used amoxicillin yet and how was it on your baby? She is six months today.