sharp pains in uterus. ans down leg

I'm 26 weeks pregnant this is  the second night this has happened  the pain will start off from my uterus and then straight down my leg. No matter which way you move the pain just gets worse  I'm in tears as I write this. I don't know what this is  or if it's serious but if you do know what it is please tell me so I do know the pain is so bad I wanna puke   But it's not intense like somebody stabbing you with a 1000 degree  knive  then running over with a steam roller but it  is very painful