Baby movements

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I'm 25 weeks 1 day, and with my first baby. She has been kicking since 20 weeks, and they're very noticeable... The last few days she barely moved; or hasn't moved at all - I've been to the hospital (advised by my midwife) and they found her heartbeat, and didn't seem concerned... 
however I still can't keep my mind at ease...I've tried ice and she still isn't moving like usual.. why could this be?