Should I ask?

Should I ask my dr for another ultrasound when I go in for my 28 week appointment? At my 20 week scan the baby's stomach was measuring right on. I had another scan at 24 weeks and his stomach kept measuring 2 weeks behind. The tech measured his stomach about 10 times. I asked if everything was ok and she said it keeps coming up small and I just want to make sure I'm getting good measurements. My dr didn't say anything to me other than everything looks fine. Which confused me since his stomach is smaller than it should be. The tech said it's still within normal range but definitely on the small end. She didn't mention a rescan but I'm worried as this is the first sign of growth restriction. I've been having bleeding and I'm worried this could be related to placenta issues but my dr hasn't checked it out other than doing a spectrum exam to see if she could see blood. I feel like she's not being cautious enough. Should I demand her do more? I just have a feeling something isn't right