I Am On My 6th Week Now, Doctor Will Ultrasound

I am on my 6th week now, doctor will ultrasound me this coming week. First time I checked using pregnancy test kit, I was negative. Then, after two weeks, I was positive. Now, I am feeling sharp pains at the lower abdomen. A week ago, I am having UTI and stopped antibiotics at 3rd day when I found out from pregnancy test that I am positive.

The thing is, the other day, I felt nauseous and morning sickness. And now, I don’t anymore. Should I worry?