Biggz, when I was 15-16, i was hella off beat. Real bad. I used to get made fun of for it. You just gotta start paying attention to how words fit a beat. You can either stay with the beat by using less words, or you can stay with the beat by changing your speed and flow. You'll get it. Don't let anyone discourage you man.
Lemme be the first to say this: None of us suck. We're just beginners.