Alamak, memang common lah kat 30 weeks ni, tummy tightening and cramping tu biasanya Braxton Hicks contractions mixed dengan pregnancy hormones yang buat perut keras-keras, plus constipation yang mmg common masa pregnant. Tapi since the cramping sampai rasa nak menangis sakit tu, I'd suggest tanya your gynae just to make sure everything is okay, especially to rule out anything yang perlu perhatian. In the meantime, minum plenty of water, makan foods kaya fibre, and jangan tahan-tahan kalau perlu pergi toilet, sometimes the pressure itself makes it worse. You're doing well, mama, tinggal sikit lagi je!