Hi , Since you have a history of constipation
, the lump you feel protruding at anal verge might be a hemorrhoid(piles) .You should try avoiding constipation by taking high fiber diet and maintain good hydration . In case it does not helps , try taking some laxative. In case the hemorrhoid protudes with straining or while defecation or bleeds, then you might need to consult your physician. Hope it helps.