Sayang, please go to the hospital or see your doctor today, okay? Diarrhoea with belly pain and tightening at 34 weeks needs checking to make sure baby is okay, better safe than sorry at this stage of pregnancy. If it's during office hours, your klinik swasta can do a quick check, but honestly, most of my mum friends went straight to the hospital labour ward when something felt off like this, they just want to monitor you and baby properly. Don't wait or guess, just go lah. Take care!