Ay congrats sa twins, mama! Belly pain during pregnancy is pretty common talaga, especially with twins kasi more stretching ang uterus mo, pero since you're 13 weeks pa lang and may normal heartbeat at walang bleeding, that's a good sign, still, best to message your OB just to be sure kasi peace of mind lang yan at importante lalo na sa twins pregnancy mo. A few of my mum friends who had twins said the cramping and discomfort during first trimester was normal for them din, but they all checked in with their doctors para ma-rule out any concerns, so go ahead and reach out to yours okay?