If anything strange is happening eversince you saw the tombstone, call a Paranormal Acitivity team. Hauntings usually occur when someone dies in their house. For example, if someone commits Self Delete in thier house. It is possible the house will be haunted.
EDIT: I meant to say if someone commits Self Delete in thier house, he turns into some kind of ghost and does not leave the home unless a prayer is spoken to protect the house. But seriously, call a Paranormal Activity Team that are experts at ghost haunting. One should usually have a cristian.