Come on Wilson lets try to get that belief back into you. Firstly think about really good matches you have played in the past where you have come off court and thought to yourself, yeah that was a great showing from me. Get all the negatives thoughts straight out of your head and look at what you've done well in the game. Everybody goes through a tough patch and this looks to me as if this is what you've hit, so you just need to keep playing hard and really enjoying it and concentrating at all times to get the best out of your game and you will see the results. Also the fact that the High School season has finished may be a factor, you may lack a little motivation for a couple of weeks, knowing that you don't need to play events right now.
You've posted on here before now how you have been really pleased with aspects of your game, your forehand, serve, footwork and your backhand you say wasn't bad recently, so you know that you can do it, as you've done it in the past, you've just lost a little confidence in your game and mentally, so your in a stage of a let down. It's simple that you've played good matches in the past, so now you just need to keep working on the practice courts, regaining some of that confidence and believing that you are a good player and somebody who can improve much more. Never ever doubt yourself at anytime, you don't become a bad player just like that.