Popping in for a belated pep talk.
Weight: with both my pregnancies I found I'd leap up 6lb in a week, work out what I'd be by the end at that rate, have a flap, worry if it was too much/ too little/ just right. Then I'd gain nothing/ more slowly for what seemed like ages- apply even more worries. In the end I gained 2st first time round, nearer 3 second time (but lost 3/4 st vomiting second time and half a stone first time- bleurgh). It sounded loads to me, but I've luckily had to do nothing to lose any either time.
Scans: its all different once you can feel movement. You get to know the baby's normal patterns. If you're worried about decreased movements ever, they'll always check you. I was scanned by a consultant (who happened to be in, not called in specially) for reduced movements at 11pm on a Saturday night once. I still found it stressful with the dts, because central movements I couldn't be sure which baby was moving. Deep low right I knew was Dt1 and he never stopped moving. Dt2 would go quiet. I felt nothing I could be sure was him for 3 days once (this lead to the 11pm scan, at about 23 weeks, my consultant said hb useless for twins then too hard to be sure you've heard both). This continued throughout the whole pregnancy. I had ctg's for him later, lots of them, and nearly admitted once. It was partly as Dt1 stayed head down throughout but Dt2 turned head down to transverse to breech to headdown (at 37+2, only confirmed at my cs though I told them he'd turned-OUCH to a twin turning at that size, he was breech at my 36 week scan) but partly just him. Dt1 never stopped moving, still doesn't. Dt2 is much quieter and calmer. Funny how it showed in utero. So once they're moving you'll feel better ad you'll know they're ok. And if you're not sure, there's always the opportunity to be checked. always .
And I could never relax, not til my baby/babies were in my arms, so also don't feel guilty if you don't 'enjoy' pregnancy ad such. It's a stressful, uncomfortable, anxious time for me. Means to an end. Shame I didn't enjoy it, but great if you do, fine if you don't. It's finite. You'll get your baby/babies. Brookety brook.