I can relate. I had a heck of a time when I was just starting hitting the strum consistently. Hit it right once or twice and then it was like my hand had a mind of it's own; suddenly I would be all over the place.

I think what has helped me is that once I got a little more comfortable with holding the chord down, I was able to concentrate on the strumming. When I was first starting, I was paying more attention to my left hand and just sort of putting my right on auto-pilot. Clearly, it was not ready for that.

And I know this sort of advice always made me cringe, but it will get better with time.

Oh yeah, how far away is your fretting hand from the strings? It could be a question of hand position. When I am playing the acoustic, I tend to kind of arch my right hand a little bit. When it's on the electric, I try to rest the heel of my hand right on the bridge (unless I am playing up the neck). Once I found a comfortable and consistent position for my hand, it seemed to improve quickly.

Just a thought.