Here is a great idea that a very good player suggested as an easy way to determine if your delivery is in fact an issue. Anyone interested, do yourself a favor and try it if you want to learn a ton about your stroke instantly.
Throw a dozen balls on the table. Completely disregard the pockets. No pocketing of any balls. Simply choose any of the balls on the table, and shoot the cue ball at it, at NO ANGLE, completely straight.
Forget pockets, drive the balls into rails, drive them into other balls, it doesn't matter. Just pick an OB, decide what is needed to hit it straight on, no matter where it ends up going.
What does matter is stop your cue ball DEAD each time. Short distance, long distance, any ball, any position. Just simply shoot to stop the cue ball completely and totally dead.
No angles involved here. Everything is straight on. See if you can stop your cue ball dead each time. If you can't, then forget all that geometry, and work on your delivery because you're not hitting the cue ball where you think you are and the most accurate estimation of a pocketing angle isn't going to matter a hill of beans unless you can hit it there.