Another thought for you to consider:
1. purchase a premade tapered leader to rule in or out the leader itself as the issue;
2. If you still have a problem with curving, then it is possible that at the end of your fore-cast, you are twisting your hand either left or right. If this is the case...concentrate on keeping your thumb directly behind the rod (cork)....if casting at an angle also try and keep the thumb in that behind position. Make sure that your thumb is not left or right of center.
Sometimes this is easier if prior to casting (if you are a right hander), cocking the bottom of the reel towards your body a bit.....this makes it easier to keep the thumb in the right position.
Try not to shoot the lie at the water....if on shore, find a treeline across the lake or stream and shoot at the tops of the trees (or as if you wanted the line to land 8 ft above the water)...you want the line to go out not down...it will do that by itself :-)
By the way.....don't be embarrased....casting is like golf.....only 10 percent ever shoot par, the rest of us have problems...just enjoy yourself.