How far along am I?

Based on my lmp I should be 28 weeks along. But I got my first ultrasound last week and they said I was only 23 weeks. So I'm now 24 weeks. I feel like I'm farther along than 24 weeks. Baby is kicking super hard I'm big but not huge. I'm just confused. This is also my 3rd child. I got pregnant 2 months after my 2nd. According to lmp. So would you say I'm 28 weeks or 24? I'm so confused. 😕 lmp was January 10th.