You need a straight, repeatable stroke. Waggle around with your practice strokes and get the shot lined up with the cue stick moving straight - no lateral (sideways) movement. When you're ready slowly draw back straight (maybe pause a bit) and then go through the cue ball straight. Straight, straight, straight. Sound easy - it's not. It takes LOTS and LOTS of practice. Watch some videos of the pros - it's uncanny how straight their stroke are, try to copy them.
BTW, I'm not an instructor but I shoot a lot better thanks to some lessons (Scott Lee's my man). A pendulum stroke and someone qualified to teach will straighten you out. When things aren't going right it's usually because of the straight, straight, straight rule. Clear you mind, get comfortable and do it straight, straight, straight. There's an SPF 'mantra' I use my instructor taught me to keep me straight - very useful.
BTW, I'm not an instructor but I shoot a lot better thanks to some lessons (Scott Lee's my man). A pendulum stroke and someone qualified to teach will straighten you out. When things aren't going right it's usually because of the straight, straight, straight rule. Clear you mind, get comfortable and do it straight, straight, straight. There's an SPF 'mantra' I use my instructor taught me to keep me straight - very useful.