Pain in the back of my leg

I woke up this morning with a pain in the back of my leg around my knee. It’s not the whole way down but more like the size of a tennis ball. It’s worse when I lie down. I do have Sciatica but it’s on my other leg, it runs the whole way down the back of the leg from like my hip right until under my foot. Any idea of what it could be? Just normal pregnancy or something else?