Twins Whats normal and what’s not?

So I’m 18 weeks with twins I thought I should be feeling them by now but I’m not. And I’ve had insane pelvic pressure all last week that sent me to the hospital on Saturday babies where good and strong heartbeats and then on Monday all the pressure went away and Iv been feeling great then today so pressure is back. Is this normal? Is it normal for you to have days where you don’t feel pregnant at all and then days your feeling like a beached whale cause you’re so bloated. I’m not showing yet because I’m overweight but I’m just worried that they are in distress or something or worse.