Markl if it makes you feel any better... I was "doing" 3plates, before I was actually doing 3plates. Had my horrible form, depth pointed out by a friend and lowered the weight, went back to the drawing board.
I know paused squats were discussed earlier and you might actually benefit from those with really light weight, like 135lbs. It'd increase your strength coming out of the hole, but more importantly it'd ingrain in your mind/body where parallel and deeper is for you so when you're squatting you don't even have to think about if you hit parallel or not. You'd know straight away.