If it's a sharp pain on one or both sides (depends on what you're doing, but could be both) it's prly ligament. Esp if you're twisting or bending at the time. If it's a constant ache, you may have pulled one or both of the ligaments, but that's less likely - having 2 little ones running around could make it more likely that you're straining them.
But, as you describe it, it could be ligaments. If it causes cramping all over or something, it could be something else. Don't keep it from your doc if you're concerned, but don't let him scare you, either.