What more could I be doing to improve in my art?

I love to draw. There's nothing I love more! But I've only been working on it on and off for the past 3-4 years, and desperately desire to improve. So, I try to make time every night (though this is often not possible, due to schoolwork and other chores) to just sit back and draw. When I do so, I always use a reference. Also, I draw during every available moment at school, with no reference. My question is, aside from what I have been doing, what are some other techniques I could use to get better at drawing? I only draw a specific style, and don't have any desire to improve anywhere else, what other methods could I use than just referencing, or is more practice all I need? Hope this makes sense. Thanks.