I'm 36 years old I been having stabbing pain on right side of pelvis? What can this be.

Many things. Unfortunately without more specifics or having the chance to examine you, this pain could be related to many different problems. It could be related to your appendic(like appendicitis), ovarian cysts, tubal infection, pregnancy!, right sided colon issues and even a kidney infection. If the pain is severe or you are having nausea, vomiting, fevers or blood from anywhere please seek urgent help.