Ob-Gyn questions? Ask a gynecologist online.
All ultrasounds have an error margin - in early pregnancy, it can be only one or two days, but in later pregnancy, it can be be as much as 2 weeks.
In your case, at 36 weeks, it us quite possible for the usg to show 34 weeks even when the baby is absolutely fine and growing well.
If your amniotic fluid is low, then yes, drinking plenty of fluids and resting will help increase the amniotic fluid level.
Fro the description of your pregnancy, I do not think you have any cause for concern
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