Confused

Just had my first ultrasound. I’m said to be 6 weeks today going by my last period however all we could see today was a sack... he didn’t know if it was hiding behind it or what. However when he looked at my uterus you could see my bladder above but there was also fluid below it as well. He’s worried that the baby got stuck in my tubes.... I’m so confused lol. If that’s the case shouldn’t I be having a lot of pain and bleeding? I cramp here and there but when I drink a lot of water it doesn’t happen. When I do cramp it’s right above my butt and its mild-moderate. Could I just be too early. He named off all the possibilities... 1. I could just be too early. 2. Baby could be stuck in tubes or 3. It could be hiding behind it. Help.