Thanks for the query.
According to your description there is possibility of herpes
or genital warts
Sometimes bacterial or fungal vaginal infection
So you better once consult gynecologist and undergo local examination and if needed you can go fro vaginal swab for culture and sensitivity.
By these the actual cause of your problem can be find out and treatment can be given accordingly.
Your spotting could be side effect of depo, usually it will subside by its own.
If not you may need additional cover of hormones to control spotting.