Since it's happening with all of the bows you shoot, I'd say it's form related. If you do a search in the "shooter's form" forum, I posted the same question quite a while back and Moebow replied with all the answers I needed. I can't explain it anywhere near as well as he did, so I won't try. But I will say that for me, my bow hand was the culprit and after doing what Arne said to do, it stopped happening to me. I'm posting this from my phone, otherwise I'd try to elaborate.
Hope this helps some.