It is normal for months to go without a period and then bleed suddenly with the Depo-shot. Yet, it is always good to be watchful and get periodic examinations by a specialist. I would ask you to have a check up and a sonogram, preferably in the trans-vaginal route. Pregnancy
should always be excluded in any case. It would be better if you can get the serum beta-hCG
titres as urine pregnancy tests
are usually of not of much use in your case. Hope this helps.