Bigmac, I see no one has answered this question. Personally, I'm not real sure what you are talking about when you say you wrap your arm around the back of your leg. Maybe a video would help.
The only thing I can think of is that you drop your throwing arm way low and behind your back. Not real sure. If you do that and think it is messing up your timing, maybe you wind up draging your arm. Try keeping your elbow at shoulder height when you take the ball back. Your forearm can hang low, but keep your elbow up.
Once again, not sure if this is the problem as I can't get my mind around the concept of "wrapping your arm around your leg". Like I said, try posting a youtube video of yourself pitching so we can get a better idea.