Blood clot???

I woke up this morning, stepped out of bed...terrible pain that wrapped around my lower right leg,  not the calf. It hurt with every step I took. I cannot squat down either. Pain subsided during the day, but then returned after sitting while my class was taking a nap. What the heck could this be??? It doesn't feel like a Charlie horse which makes my muscle sore. A Charlie horse would have woken me up in the night. I'm freaked out...I'm 28 and & weeks pregnant.