Hi,
Just to reassure you - proctitis can definitely cause right sided abdominal pains and abdo cramping - I have experienced this and a recent scope only showed proctitis this time. The cause of the pain isn't inflammation as aside from rectal burning, inflammation itself doesn't usually cause pain - it's bowel dysmotility and spasm which can occur proximal to the inflammation.
Hope this helps. Also although with proctitis the inflammation is limited you can get all sorts of symptoms which can fluctuate markedly ranging from severe diarrhoea with urgency to normal stools with a hint of mucus.