Hi P., breastfeeding and starting back on periods is very specific to each individual. How long did you breastfeed, and if your baby is only 5 months old, why did you completely stop? Or, are you still occasionally nursing? Do you still have milk? The hormones in charge of making milk may still be working, and the hormones to get cycles started again are probably ready, but not yet in full motion. Are you sure your're not pregnant? If you have not been using contraception, that could happen. If you used Depo, that would be another reason for no period yet.
Talk to your provider about your next step--you may need to just be patient and wait until a period starts. Just don't get pregnant if you don't want to yet!
K. V