could be an ovarian cyst. after you ovulate the whole the egg came out of becomes an organ called the corpus luteum. It functions for two weeks producing progesterone in case of a pregnancy. When no pregnancy occurs it breaks down and goes away and your period start. Sometimes it becomes a cyst and continues to produce progesterone which can delay your period from a few days to a few weeks or more. They usually go away by themselves.
In my opinion, 2 weeks late for AF and no BFP means probably just that...negative. Seems like maybe some menopause issues (my mom actually started all of that around 40) or seems like a cyst because of the pain.
Best wishes (and try not to stress, AF could be late because of stress, too).