I had slipped from stairs around 2 months ago and since then I am having lower back pain. Kindly suggest. My age is 26 with slim body.

See a doctor. you must bruise a lot of muscle and possible you might broke your tail bone my advise see a Doctor can examine you either will assure you or treat you do not ignore it sometime simple problem might go away with a simple treatment go and see a doctor for evaluation good luck.