I had a c-section 9 weeks ago an only bleed for 3 weeks since then i have not had a period i have very painful cramping an lower backache?

See your Doctor: Although probably nothing serious, this needs to be evaluated.

Many options : Irregular periods are one of the most common problems obgyns treat. If this is one time problem it usually resolves on its own. If this is a recurring problem you should be evaluated. Infections & hormonal changes can cause spotting. If there is a concern for pregnancy then do a home pregnancy test . There are many options available to help regulate the menstrual cycle. Schedule a visit.