You can easily force yourself to draw to get better. You may not put forth the same effort, but any drawing counts, as long as you're actually paying attention.
If you want to do comics, even if it's a really low paying job, I suggest something like SCAD, or some schools in New York. Mind you, you don't have to go to an art academy at all, there are some really great community colleges that offer college level studio classes. Which, in the end, is mostly what you're getting at art school, without the liberal art classes.
There's really no tips outside of what's said except make sure you have the time to put forth. This isn't something you can do 1-2hours a day and be done for that day. Art Academy's put workload on you to the point where it seems impossible to get anything higher than a C in most of your liberal art classes. You're in high school, a pretty good age to start drawing.
If I suggest anything, it's to stop doing fanart and focus mainly on getting better at the basics and foundation. You don't have to stop, but it's what I would do in that situation. Study for most of your time, and then draw everything you learned that day into something you're going into. For example, if you do a day of figure studies, design a character focusing on what you learned. Then the next day do the same, but focusing on things from that day, and the previous day. Then the next, etc.
Senior year for the most part, should be pretty easy aside from finals, spend the rest of your time focusing on figure studies, this is where your portfolio will focus on if you want to get into any art school. Though again, I don't see the point unless it's something like Animation or Game Development.
On to your drawings, it seems like you're just drawing what you see, without actually doing any measuring. You could use a grid or measure with your pencil to get the drawings to look more of the reference. Don't be afraid to erase, if something doesn't match up, erase it and do it again, sadly I don't follow this rule enough.