I never in my life had gotten a charliehorse until I was pg. I got them every once in a while in my calves. From what I read it doesn't seem like there is a difinitive answer to why it happens. But I did read about calcium deficiency and a few other things. I would say go for the extra milk. It can't hurt. I think I also read that it could be related to potassium so maybe have a banana with it.

Hope you feel better soon. It eventually did go away for me.