Even after 10+ hours of practicing on the range, I still can't reliably even make proper impact with the ball. Help!

Hey! So, I'm new to the game, as you might have figured out by the title. Anyways, I started last fall with a basic beginners course, which is mandatory where I live, so basically a pro taught me the basics for 12 hours or something over 2 weekends. And this spring I started practicing after taking a break over the winter. I go to the range almost every day(as well as putting green), and I've probably shot like 15-20 buckets or something, but I still don't always even make contact with the ball. Very often, I hit the ground way before the ball, or I top the ball, or sometimes even hitting over the ball. What could I be doing wrong? I figure that I'm somehow changing my stance mid-swing, and that's why I'm not hitting where I started my swing(by the ball). What could cause this? Any tips to improve it?