I don't have any advice, but a little reassurance that it isn't always a sign of the more sinister things we're always afraid of when we see head banging. My DD2 was a real head banger from, ooh, 7 months? Temper, frustration, DD1 getting something she wanted, not being allowed to play in the toilet water etc. She has only recently stopped doing it (mostly) now she lies on her back on the floor with her sad little face till I come over (much better reaction). In our case, I was feeding it by my reaction - it took all my strength to ignore it and not look/react/stop her from hurting herself until she'd stopped and pretend I hadn't noticed, as with this one, she doesn't seem to mind a negative reaction either. I then went over the top with lashings of attention and rasberrys and googling if she gave any other reaction - hence the lying on the back thing now. You could try something similar. It's so hard though, especially when they constantly have a bruise on their forehead! Talk to your health professional about it if you're concerned, or there are other concerning behaviours associated with it. Hope it stops soon for you.