Let me give you the long, horrible, background:
Currently I'm about to be a sophomore in high school. At the beginning of last year, I was put on lead for my high school big band (not because I had good chops, I didn't, but because the other trumpets had even worse range). The parts were way too demanding for me at first. So I spent the year getting into lip slurs and long tones. My range started to get really good really fast: I started the year with an inconsistent high D/Eb (above the staff) and by April I had a strong high A above it and was able to squeak out double D's. Soon after this peak, my range began to go down, FAST and HARD. There were moments in May and June where I couldn't even hit a solid high D, and my range was literally no better than it was when freshman year had begun. My trumpet teacher said that this was a problem with embouchure tension, that I was tensing my corners before I put the horn to my lips and this restricted my lips from buzzing sufficiently. I spent a solid 2 months, from May to July, doing relaxation exercises like pedals and soft playing to practice being able to relax my corners. I was eventually able to transfer this to my upper register, and to this day I still don't have a problem with tension.
So after I fixed this, my range was still as horrible as ever because I had to stop doing range exercises to fix it. I started again with the lip slurs, and then just about 2 weeks ago I started with arpeggios (specifically, the exercise found in this video How to Play High Notes On the Trumpet! - YouTube). This improved my range tremendously, going from a weak high E when I started 2 weeks ago to a strong high G and squeaks of higher notes just a week later. Then, on a particularly good day (this was 3 days ago), I got a little excited with my range and played around with my upper register for quite a while, playing high lead charts and high solos. The next day, my tone suffered ridiculously. I cannot even describe in respectful words how my tone went to crap in that one day. My tone had actually gotten decent (I play on a lead mouthpiece, so it's hard to get good tone, but I had gotten it nevertheless), and the next day it was comparable to a 3rd grader who uses too much pressure. Not kidding. My range also suffered, but not as much (it went down to a strong F). I realized immediately what the problem was, and that day I didn't burn out my chops on high notes (in fact, I only played above a high C when I was doing the arpeggio exercise). I hoped that because I didn't over exhaust my upper register but I still did the exercises to build it (lip flexibilities and the arpeggios), that it would be better the next day. Was I correct? Far from it. The next day (yesterday) my tone was even WORSE yet, and this time my range had really gotten bad again. I was down to a very weak high F and even my D's were getting inconsistent. I did the same thing as the previous day.
Now today, I have just begun practicing and noticed the same thing. Not only have I still not improved, my range is back to where it was before all of this crap started (weak high Eb) and my tone is still disgusting. All of this up and down is really making me angry. I love playing trumpet (or at least I did), but this is making me just want to quit. Even my teacher (who is a professional) isn't 100% sure of my problem, as he keeps giving me solutions that work only for a short time. I can't put into words how frustrating this is, how much I hate trumpet and my life, but I have no motivation to continue if this doesn't get better.
My practice routine for the past 2 weeks: Lip trills out of Advanced Lip Flexibilies by Charles Colin, arpeggios (the ones in the video), long tones, then improv. I had been careful and made sure to rest as much as I play, resting a short amount of time between individual exercises and taking longer breaks after the arpeggios. The Colin studies really helped my flexibility and the arpeggios really helped my range (and tone, I found) but it's all gone now, ONCE AGAIN. Can anyone help me?