Ay ganyan din ako around that time, girl, parang ang tigas ng belly ko even when sitting tapos yung sakit sa pusod area, nakaka-alala talaga! From what I've heard from a few of us, could be ligament stretching (yung round ligaments tumatagal mag-adjust) or even Braxton Hicks na nagstart na, pero honestly mas better kung i-check mo sa OB mo para sure, lalo na kung may cramps or unusual discharge kasama nito. In the meantime, rest when you can during commute, maybe get a proper maternity belt or pants na designed para sa preggy kaya hindi mo na kailangan mag-unzip, mas comfortable at safe para sa baby mo. Pero definitely mention this sa doctor mo on your next visit ha!