If you feel extreme pain in your abdomen area, or are experiencing bleeding, please please go to the doctor. If you don't feel your baby moving like he usually does, it should raise warning alerts to you too.
I know there are some mummies that have their gynaes on speed dial and whatsapp them for little reasons just to have a peace of mind.
For me personally, as I know my body best. If I sense anything amiss, I'd go to my gynae. If my baby wasn't moving, I'd lie down very still. Usually, I can feel him move that way ^^