Hi, I've Been Having A Weak, Shaky, And Aching Stomach

Hi, I've been having a weak, shaky, and aching stomach for about few days. Every time I would eat something my stomach would start hurting. So I thought maybe it was indigestion, so I decided to take 4 tablespoons of castor oil as instructed and wait a day to see what would happen, and fortunately, I did have a very good bowel movement but still my stomach is kind of on the shaky side and I have sharp pains in my rectum. So I do not know what could be the cause...