21 weeks pregnant

Im at my 21weeks now. Yesterday i started to have cramps more like a painful cramps frm my below tummy to my vagina & anus in the afternoon. I can't seem to walk properly cos it hurts so bad but after a few minutes, it's gone. But at about 11pm, it become worse tat i can hardly move or walk. I lay on my bed & fall asleep but about 230+am, i awake up with another cramp. Need my husb to help me. Wanted to go to hospital but the pain is still bearable. Cramps come & go till afternoon. Is it normal?