Depo shot and no period

Am I the only one on the Depo shot but doesn't comes on their periods... I've been taking it off and on...I've been missed out on lots of periods for two year now...but last year 2013 I had a baby my husband and I didn't plan on having another baby... He just popped up one day I call him my surprise prince...but I'm back on it took it after I had him in march he's one and the last time I had a period was in May of this year but havent had a period since and I'm not expecting.