Hello, I had an ultrasound yesterday. The midwife thinks it's 32 weeks…

Hello, I had an ultrasound yesterday. The midwife thinks it's 32 weeks The ultrasound was on 29.4 days Heart rate: 133-140 I'm worried because they said my heart is strained. I read online that some people say 120-160 is normal, while others say 140-160 is normal. I'm also worried about the due date, there's too much discrepancy. But the doctor said that development is good, but she said there's some strain on my heart.