Hindi pa rin basta-basta normal yan, mama, I'd really suggest checking with your OB para sure, lalo na kung twin pregnancy mo kasi mas importante i-monitor ang bawat baby closely. A few of us mums with twins here, and most namin nag-feel na ng movements around 16-20 weeks, pero every pregnancy talaga ay different, especially kung first-time mo pa lang or kung anterior placenta mo. Kaya better safe than sorry, let your doctor assess kung okay ang positioning and heartbeats ng both babies, hindi ka dapat mag-worry na lang on your own.