yes, it's fine. everything in pregnancy is normal unless you're excessively bleeding and losing a limb
This is so not true. At all.
OP, cramping is probay normal. Make sure you are well hydrated and take it easy.
Ditto this. It's probably nothing, but if it comes and goes definitely call your doc. I know several twin moms that have gone into PTL before viablity and have lost both babies. A girl I'm FB friends with has a sister that's 22w pg, at 21w she was having regular contractions, tried to get a cerclage, didn't have enough cervix for the cerclage and her water broke later that day. Luckily it was just a trickle and is still pg, her water has refilled, but they're taking it day by day. Not trying to freak you out, but you definitely need to let your doc know if something is different than what you normally experience.