The 17th week of pregnancy has arrived. I feel uterine contractions to…

The 17th week of pregnancy has arrived. I feel uterine contractions today, I don't understand if it's stretching or not. The uterus feels like it's pulling and fading. I have an appointment on April 20th for a second ultrasound, should I see a doctor now or is this normal? I haven't done anything physically, except for the unusual. And the question is, such contractions sometimes happen after sex. But they pass through in 5 minutes. I feel the same contraction today, but there hasn't been sexual contact for 4-5 days.