I had an ultrasound, they didn't find a fetus in my uterus and they ca…

I had an ultrasound, they didn't find a fetus in my uterus and they can't put me on a non-uterine pregnancy either because there's nothing there either. But on the left ovary there is yellow fluid. Maybe someone has experienced this, you're all good, did the fetus get found after? From a medical perspective it's 6 weeks but according to my calculations it's week 3. The doctor also said that the term might still be small and sometimes at 6 weeks they just don't see the fetus yet. But the ultrasound did find a black dot, they say maybe this is the fetus. In general, have anyone experienced this, tell me what happened to you afterwards.