BV is especially noted for being smelly on or around the period, though it is often said to be smelly at other times as well. My guess would be that you have BV. For that, see your doctor, there aren't effective home treatments. Also, your boyfriend should be on the same antibiotic as you at the same time, so he does not inadvertently pass the bacteria back to you.
Hm, I've not heard of depo doing this. when is your next doctor's appointment (we should all go once a year for a well check)? This would be a great question for that appointment. And sincerely, I hope you come back and tell us what they say. I think of bacterial vaginosis when people talk about rotten smells--- but it would be unusual for you to ONLY have the odor when menstruating. good luck