One of the most comforting thoughts (for me, at least) when these things are troubling me knowing that someone out there has it worse than me. I'll be the person you look at when you want to feel better about yourself.
I'm 15. I used to take 4-9 pills a week (as in MDMA) as well as Concerta, IR and XR, codeine (to come down), and about 300mg of dexamphetamine. I'd spent ?700 in about 3 months. One time, I took 9 250mg pills and .75 of mandy (MDMA powder) in 3 days, and in the end my kidneys had become so damaged that I was accumulating fluid around my limbs. I would be up for an average of 4 days at a time, the longest being 11 days, only deciding to sleep when it looked as if my quilt was crawling with spiders. I ruined dozens of potential relationships because I had either been up for days and was acting weird, or because I was in such a state of craving that I just couldn't talk. I almost developed another eating disorder. I hallucinate on a daily basis now, my anxiety is worse, and I hate being awake. It got to the point where every time I took any any amphetamine I went straight into amphetamine psychosis. I would see spiders coming from the ceiling and every time I took an upper I convinced myself that the left side of my face was paralyzed. My gums receded and my teeth went yellow. I can barely get myself into school without a drug of some kind to make me more confident or less anxious. At the age of 15.
In my experience, the only way to finally get over an addiction is to hit rock bottom and completely run out of the drug or means of paying for it, but that's coming from me, someone who just takes pills and considers the consequences later. I hadn't been using drugs this heavily for too long, I lasted about 3 months before I burned out. For that reason, I think your abuse is as bad as you think it is. Taking 300mg of XR amphetamine isn't a particularly high dosage IMO, being that it lasts about 3 times as long, and a friend of mine took 60mg his first time. Maybe if it is really bothering you, then quitting would be in your best interest, but as far as permanent damage goes you're safe.
Honestly, I don't think I'll ever get better. Once you've went on speed binges and taken pills every other day it's far too difficult to stop without simply running out of resources first. I think about amphetamines constantly, and as soon as I get any money in my hand I get myself as many pills as I can buy. This isn't a universal position when it comes to addiction, but you might find out you're just the type of person who wants to be fucked all the time. I'm like that too, and the stupidest things can remind you you're sober, so if you plan on quitting you need to take up a hobby so that you can preoccupy youreslf with other tasks. Something phsyical is better than something mental, so stay away from something like learning a new language or reading. The mental strain will probably make you want to start up again. For me, it's as simple as just going down to the park at the bottom of the street and going on the swing for an hour or two to work out the frustration. I don't know if you've experienced the frustration I'm on about if you haven't quit yet but you'll know exactly what I mean when it hits.
BEST OF LUCK