Sayang, please go see your doctor or call them today , 6 days of cramping + diarrhea during pregnancy needs proper checking, even if it feels like gastro. Better safe than sorry, especially since you're 21 weeks and it's your first baby. Don't wait lah, just go! A few of us mum friends have been through gastro during pregnancy and memang kena see the doctor to make sure it's not something else affecting baby. They can give you safe advice and maybe check your baby is okay. Jangan worry too much, but don't delay also, pregnancy + ongoing symptoms = doctor's job to assess, bukan DIY. Rosakkan sikit je your day to go, tapi peace of mind tu priceless!