Hi! I'd like to help you with this concern! Unfortunately, yes, this is probably just a side effect of the Depo shot. Many women take up to 6 months to adjust well to the injections/hormones and have all sorts of irregular bleeding patterns. Too bad you were not one of the women who do not have any period at all!! The dark brown/black spotting suggests that there is only a slight amount of bleeding and it is taking a good while to come on out, causing it to turn brown/black, like dried blood. It then mixes with the normal vaginal secretions and comes out as spotting. If you are sexually active, I encourage you to consider taking the shot just one more time, because you may adjust this time, and actually have little or no priods later. It would be normal for you to have the cramping, as this would be when you would expect to have a period. Since you bled for 2 1/2 months, there would not be much build-up of ther uterine lining to shed now, explaining the spotting. You may want to consider the BC patch or the nuva ring. These are good options to discuss with your GYN if you do not intend to take the shot again.
I hope this helps! Let me know if you need more information! Please click ACCEPT! if this answer is helpful! Donna RN (positive feedback is HIGHLY appreciated!)