Hi, congratulations for having twins. Coming to your problem, I don't know weather you are breast feeding your babies or not, as some women stop having periods if they are feeding their babies, others may have irregular periods
as ovulation will either stop or become irregular & so is the period. This is normal physiology and will settle on its own. If you want to be 100% sure that there is nothing wrong, get one serum BhCG checked ( it will be a blood test
) & show it to your Dr.If u really want to regulate your cycle then you can discuss with your Dr about starting "pills"rather then depo shot, as it is more likely to cause irregular periods. Type of "pill" will depend weather you are feeding your babies or not. Good luck.