Worried...

Daniela • Mom of a toddler girl excepting my baby boy July 2016 💙💟
So I had my Scan at 20 weeks last month and the lady asked me to come back in 4 weeks because she was not seeing everything she had to bc it was not clear enough. She asked me to drink a lot more water which I tried doing not always with success. Yesterday at 24 weeks and 1 day I went back again and she was able to see everything and the baby looks healthy but told me that she was worried because I had less fluid then before that i needed to keep drinking more water which I am but that's all she said. I have another scan in 4 weeks to measure the fluid but I can't stop worrying... does it mean preterm labor? Does it mean my baby will struggle? I am already a worrier and now I basically beg my baby to move in my belly. Has anyone had this happen before?