Kept having weird pressure in my lower abdomin and random sharp pains yesterday. I had to stop what I was doing because it hurt so bad. Is that just ligament pain or should I be concerned?

Also I'm almost 17wks and was wondering what it feels like when the baby moves. I was sitting on the couch yesterday and I felt something flip in the lower part of my stomach. It was a very strange feeling. I didn't know if it was the baby or maybe gas. Even though it didn't feel like gas......