Aw mama, I understand the worry kasi first time hearing this from your OB! So it's actually normal na mas maaga mong ma-feel ang movements sa second pregnancy because your uterine muscles already know what's happening, plus yes, thinner abdominal muscles mean you feel baby earlier, a few of us moms with similar situations noticed the same thing. The good news is that your skin and muscles are actually super stretchy and designed to accommodate baby, so it won't "rupture" even if you show earlier or baby moves a lot, pero since your OB specifically mentioned this about your muscle thickness, definitely ask her directly kung may specific precautions ka need to take or if there's anything to monitor throughout your pregnancy, because she knows your full medical picture. Don't stress yourself overthinking this because stress isn't helpful either, and honestly mas importante na comfortable ka at baby's doing well, which it sounds like from your movements! Keep your OB updated lang sa any concerns.