Suggest Treatment For Sore Throat And Flu During Pregnancy

I am 10 weeks pregnant. I have sore throat and flu symptoms for over a week with fever last weekend, but now is ok. I was getting better until Thursdays night. I starts having swollen lymph node on one side of my throat and it was slightly painful when I swallow. I called my Dr. next day and he prescribed me with amoxicillin 250mg 3 times per day, but my the swollen got worse the next day. so, I called the on-call doctor of my PCP. She told me to take 500mg instead of 250mg. I went to ER today because My throat got more swollen and more painful this more when I woke up. The ER doctor changed my antibiotic to Z-Pack. Not sure if I should starts it or not. Is this medication safe for 1st trimester pregnancy?