Extreme abdominal pain after eating and sharp sudden rectal pain lasting. How can I relieve the pain?

Many things. Many things can cause the symptoms you are describing. If you are constipated it is a good idea to increase the amount of fluids in your diet. If you have heartburn an over the counter medication such as Tums (calcium carbonate) may provide relief. Otherwise, see your doctor for a proper exam.
Proctalgia. Proctalgia fugax is a form of IBS. We have a profram known as SEEDS which adresses all aspects of therapy. When the pain is severe try warm baths or the prayer postion. Please see our website and book "The Gut Solution".