18wks movement all over

This is my gourth pregnancy, the last one being over 8 years ago so i dont remember so well. Im 18 weeks and started feeling the first baby movement about 3 weeks ago this started about half way between pant line n navel. Then about a week ago started feeling real kicks and turns in the same area always on left side. Well over the last couple days i have felt him or her very low, up high above or around nevel atea and left n right sometimes all within seconds. Is my lil one big enough to do all that moving around or could there possibly be two?