Ahhh sayang, sakit pinggang belah kiri especially kalau sampai cramp ke kaki, you really need to see your doctor or go to the clinic asap lah, jangan tunggu lagi! Could be many things and they need to check you properly. A few of my mum friends pun pernah rasa macam tu, tapi memang kena settle dengan proper check-up, bukan boleh tunggu je. Some punya it was serious, some nope, tapi doctors je yang tahu mana satu. Go lah, babe, better safe than sorry!