I think it might be more helpful...and you might get some better advice...if you outlined what your practice sessions and schedules look like.

"I play every day, anywhere from 15 minutes to 3 hours" sounds kinda haphazard to me. Fifteen minutes is not much more than a long warm-up...it certainly won't let you do much more than get caught up with what was practiced the day before. It might let you keep fresh on what is already learned but it's hard to imagine moving forward and learning new things on such a small time block.

Establish what you want to learn/practice and assign practice time to each of those objectives. Anything less than 30 minutes a day in total is going to hold you back or, at the least, make your progress verrry sloowww. IMO.

There are lots of lessons and tips about how to practice both throughout the internet and here on GT. Here's three on GT...take a look;

How to Practice http://www.guitartricks.com/tutorial.php?input=1652

Guided Practice Routine for Beginners http://www.guitartricks.com/tutorial.php?input=1437

Mastering the Art of Practice http://www.guitartricks.com/tutorial.php?input=1194