Uy, mommy, lakas ng loob mo mag-check sa doctor agad about this ha, especially if may sakit or heavy feeling, kailangan siguraduhin na lahat ay okay with baby. Maraming causes yan ng tigas ng tiyan pag buntis, pero hindi dapat i-guess lang, kailangan ng proper check-up para ma-rule out ang anything serious. One of my mum friends had similar concerns, at napaka-relief niya pag nag-ultrasound at lahat ng findings ay normal lang. Go to your OB or emergency if parang sobrang painful na or may bleeding, ha? Better safe than sorry when it comes sa baby. Praying for you!