thanks for the query,
depot medroxyprogesterone acetate
(DMPA) is a branded progestogen-only contraceptive
Takes one week to take effect if given after the first five days of the period cycle. Effective immediately if given during the first five days of the period cycle.
So in your case , its effective from 7th day of your cycle.
Failure rate is 0.3.
Now i think you can take a decision how to go about taking minimal risk into consideration.
hope this helps,