I have to get myself together. I need advice.?

I am 16 and in my 11th year of school (which would be 10th grade). I can't really handle the workload that much because I am easily side track and I tend to procrastinate alot! Hence the reason why my parents take my phone, bedroom door, and limit my electronic priviledges for grades. My grades aren't stellar my overall is usually in the 80s (we do numbers at my school). But I just have trouble sitting still. I am getting lazy with work ironically because I'm actually energetic, but you know what I mean by lazy. I mean figurtively not literally. I am trying to take steps closer to quitting the internet but it is just too hard to quit. Here are good habits I started lately. I started reading a book, writing, drawing, and I swim. Also I am failing math right now for the 5 week grades because I bombed a test, and anyone who takes trig understands how test are so important. I couldn't study for it. I'll admit I goofed off 10 minutes after looking through notes. But after that test I been getting the help I need everyday at lunch, been coming in and getting help. My teachers says I'm going to do alot better for the quartar which is good, but how can I prevent this from happening with other subjects. I just get too discracted.