Could be several issues but get someone who knows to have a look at your gun fit. I'd put money on the stock being too low...
Definitely agree with this, it really is difficult to second guess the issue, it could be two or three faults together. I would say this though that women appear to need somewhat different stock needs and only a few coaches/fitters seem to understand the subject but bet someone like Cheryl Hall would nail it in double quick time.
In my experience tower birds are very hard to master, even a great many good shots never really get to grips with them and this despite the fact they show oodles of belly and are rarely more than thirty yards away ! This is almost certainly because you have to ultimately shoot them with tempo and sight unseen at the moment of firing. You often see good shots adopt pretty extreme methods when faced with seemingly simple incomers including firing at them a few yards out of the trap well in front or twisting around and taking them as crossers, the former particularly, is rarely 100% successful and exposes their lack of confidence more than anything.
As others have already said learning to lift your head off the comb is not an option, more than any other presentation these need prior thought on your part to assess your own particular sweet/kill spot. Too early and you're just snatching, side ways is OK at times but if the clay is directly overhead then that too is not as good as learning to shoot whilst facing the clay.
This bird needs
the line read like no other, even small amounts of L or R inclinations should be dealt with by a change in your stance. As for method the best I have found is not pointing towards the launch point but rather have the gun much much higher up, perhaps only as little as 3-4 yards below the actual kill point. Watch the bird come to you and don't move too early, you'll soon see it appears slower than you thought, watch it, raise the barrels into the space immediately behind it's trail, track it for a half second, and flip through it with whatever tempo or lead you believe it needs depending on it's speed. In my experience most tower birds are best shot when almost directly overhead, unless dealing with a pair in which case you may well need to touch off at the first one a bit earlier.
One last point, these do not need choke, anything over 1/4 is a handicap and anything less is almost cheating.
