After stopping depo it may take some time for your periods to normalize. The time varies in every woman and can be from 2-3 months to 12-18 months .The length of time you use Depo-Provera usually has no effect on how long it takes you to become pregnant. If you are not on any contraceptive you can get pregnant any time. Are you also having other symptoms suggestive of pregnancy like sore breasts, increased urinary frequency, nausea, vomiting etc? If you are doubtful take up pregnancy test. Visit your gynecologist for more queries and assistance. A clinical examination is very important. Keep me posted.
Best luck and take care!