Doxycycline - In 1 trimester

Hi everyone. It's my first pregnancy and it's my first month. 10 days ago I was put on doxycycline 100mg twice a day for 5 days.. my gynac seemed a bit concerned. My ultrasound is between the 25th and 30th. I'm extremely nervous. Has anyone has an experience with doxy before?. I need some hope. My other counts seem good.