Hormonal birth control.

I was never on b.c before I had my daughter in october.after I had her I got the arm implant.horrible choice.so I got depo in may and worked really good for two months.but now I'm sporting or vary lite bleeding for the past 9 days.I don't really need every time I use a tampon there's not much blood if any but a few hours later I wipe some off.its like I bleed for 30 mins then stop for 5 hours.is this normal with depo.or should I talk to my ob about it? Could it be I have problems with hormones in the birth control?any one else have problems,opinions on other birth control?