Whenever I'm having trouble with motivation, I go back to the basics. For me, I find that I develop unhealthy thinking habits that undermine my motivation. So by changing a few things I'm able to improve my habits with minimal willpower. It takes 2-3 weeks to start seeing significant results. The goal here is to train your brain to think differently and no amount of will power will do that, only habits will.

Are you sleeping 8 hours a night? If not, start going to bed early and consistently so that you wake up before your alarm goes off. If you have a TV/Laptop/Phone in your bedroom, remove them. Bed is for sleeping only. Kill off caffeine if you're drinking a lot. At the very least only have it in the morning. Are you eating well? If not, start. Remove junk food from your house and get healthy snacks like fruit (ask your parents for help on this).
Are you meditating? If not, start (I recommend headspace.com) Are you doing anything that is fun that is outside of your normal habits? (i.e.: not reddit) If not, do this at least once per week. Stop scolding yourself for not doing what you think you should be doing. You know it already, stop abusing yourself. Abusing yourself is obviously not working so try something different.
Instead, write a daily log of what you did each day and write down 3 things you want to do the next day. Those 3 things must not amount to more than one hour of work. Read your "next day" items each morning. Don't force yourself to do it, just put them in your head. When this starts working, you're going to stop and fall back into your current habits. Realize this, and just restart the habits. These basic are what you build on.