Considering the history of "birth" and assuming it was normal delivery or with episiotomy
(a slight incision given to facilitate vaginal delivery
) the chances are that the injury caused by the normal birth process might have developed some infection leading to a abscess
(considering the painful nature of the lump you describe). Hemorrhoids are nothing but varicose veins
of hemorroidal plexus situated in rectum
, usually caused by continuous or excessive strain usually with prolonged constipated hard stool, due to chronic coughing, or occasionally due to pressure caused by fetus on abdomen or during prolonged labour...however a history of correlation of pain with stool is usually present if at all hemorroids are to be thought of. Final diagnosis can only be established after medical examination.
Hope this gives some clarity about your problem.