Sayang, ngilu and pain down there during pregnancy memang boleh happen, tapi sebab ni bukan something to guess-guess, better you see your doctor or midwife asap, especially since it's affecting buang air kecil juga. Bisa ada banyak reasons, dari pressure je atau something that needs checking. Don't wait, ya? Your doctor kena tahu, terutama at 31 weeks. Jangan worry, but jangan delay jugak. Let us know how it goes!