i used to have the exact same problem, if you find you cant keep proper stability in your bench press you could try switching to a smith machine as well, i switched to SM for my benchpress because i had problems with my shoulders and i've found that my strength gains have been awesome since you do not have to worry as much about your stability through the lift.

and if you're wondering what a smith machine is:
it keeps the bar stabilized and its guided so you only have to worry so much on using your strength which can also allow you to lift more weights. it can also be used for deadlifts and squats if you do not have a spotter.