I am 31 weeks pregnant an the doctor said the baby is head down in my pelvic area. WHAT DOES THIS MEAN?

I work at a warehouse and I do lots of walkin at work almost daily is this one of the reasons... I also have a 3 yr old who is very active and we do a lot together. IS MY BABY GONNA COME EARLY I'M DUE MARCH 16 PLEASE HELP :-)