Hey mama, congrats sa second baby! Yan normal lang naman, lalo na pag pagod or nag-walk ka ng matagal, yung uterus mo lumalaki at nag-aadapt pa lang, kaya natatense yung muscles around it, nakaka-alala pero hindi scary talaga. A few of my mum friends had the same thing sa first trimester, pero best pa rin to mention it sa OB mo next checkup para peace of mind mo, lalo na since iba-iba ang bawat pregnancy. Rest when you can, stay hydrated, at don't hesitate to call your doc if meron pang ibang signs na worried ka about okay?