Nighttime Charley horses!

Kelly • We have a 2 year old girl, and now we're pregnant with baby GIRL #2! We're so thrilled! Due 8/21/16
I'm 30 weeks pregnant and been getting Charley horse cramps in my calves at least once a week during the night. They hurt so bad and don't know how to make them stop. Anyone else experiencing this? Any suggestions to help them stop?!