Measuring big

So my past few fundal height measurements I've measured 2cm ahead which is normal. The second to last one I was 4cm ahead and she said she'd keep an eye on it. Tuesday I was 33 weeks and measuring 41cm! I have a growth ultrasound on Monday. I know fundal height isn't always accurate but this is freaking me out. What could it possibly be? What are some outcomes?(induce?)