Aiii congratulations on your kembar pregnancy! Honestly 18 weeks is still early, you've got time to prepare your mind and body, so don't stress too much lagi. A few of us in my group pregnant kembar too, and the common thing they say is just make sure you rest more, makan enough (seriously, kalori requirement naik), and go for your scans religiously sebab doctors need to monitor both babies closely. One of my mum friends swears by getting a good support system early, partner, family, or even just trusted friends, because the third trimester with kembar boleh quite uncomfortable, and you'll appreciate the help. You're not alone in this, mama!