Ah anak, kung biglang sakit at may diarrhea, kailangan mo talaga makita ng doctor agad o pumunta sa nearest clinic para sigurado, hindi kami dapat mag-guess dito. This could be something simple or something na kailangan ng proper check-up, so better safe than sorry talaga, lalo na if it's intense or may iba pang signs like fever. Hydrate ka muna habang naghihintay, but please go have it checked out soon, ha?