Is it normal for my period to last over 12 days while on the depo shot.?

I'm not sure. I was on the shot myself (having taken it just once) for three months. I got the shot in November, and never got a second one. I had a few days of very faint spotting, and FELT like I was going to get my period two months after my second shot would have been due. One month after, I got what seemed like a normal, if not light period. Had a week following that of no bleeding at all. Now one week later, I am experiencing very heavy bleeding. If anyone else has experienced this, and it is normal for Depo discontinuation, I would love to hear about it. If anyone has experienced this and sought medical care and it is something to worry about, that would be helpful also.