muscle cramping

I'm pregnant with identical twins, 17weeks5days, and two nights ago I woke up to use the restroom and had a stretching pain in my groin area. From about my right hip to the top of my vagina (or pelvic bone) it felt like my muscle were almost tearing. It felt better to lay down. Talked to an advice nurse and she said to call if it got worse. It seemed to be better during the day with walking and moving. Got it a little bit on the left side but that only lasted a minute and was very faint. So I had it again last night and now the pain feels like a muscle cramp in my groin as the ones in my calves feel when I get those. Has anyone else experienced this?