Did you actually injure yourself/tear something or were you just getting sore or having tendonitis issues? Did you ever see a doctor and get an official diagnosis? Have you ever have your form critiqued? Lower back being super sore on squats is not a good sign, I'm assuming form break down there.

Lots of questions but given the information provided it doesn't sound like anything crazy serious. Lots of us are always dealing with niggling problems. For example I have hip flexor issues and tendonitis in my elbow and carpal tunnel in my wrist and all that. I've only been lifting for 3 years!

It's just a matter of working around an issue, (p)rehabbing it and/or resting when absolutely necessary. No one who is seriously lifting or actively involved in sports is 100% healthy all of the time. You are going to run into problems, its how you deal with them that matters.

1) Resting is fine (and usually preferred). IT band issues are pretty common, I've never experienced it but there are lots of prehab/rehab/corrective/whatever things you can do for it if you start to run into troubles again.

2) Form critique is very important I've found. I video lots of my gym sessions. There is a sticky at the top of this very group for form critique in fact. Proper technique is probably rules #1, 2 and 3 for injury prevention. I highly suggest at least videoing yourself and looking at your own form for your own purposes. Research proper form, keep an eye on yourself and you can progress VERY far without killing yourself.

Having said that, you want to lift heavy and you want to play sports. Something is going to have to suffer in there. There will have to be compromise struck. Me personally, my sport IS lifting so everything I do focuses on that and I don't do anything else that inhibits recovery. You'll have to do it differently. Progress will be slower, you can't train as often or as hard but you can still make progress. Training 2-3 days a week with a program designed for use in athletics is probably your best bet. Take a look at:

http://www.jtsstrength.com/store/the-juggernaut-method-2-0/

https://www.t-nation.com/training/531-and-athletes

As far as what "too much" is, that's trial and error. You're young, you can probably handle a lot more than someone like me. You're just gonna have to find that happy medium, that compromise that you'll have to strike to lift and play sports at the same time.

Lastly, counterproductive is the exact opposite of what I would call lifting and sports. Being strong will make you a better athlete, period. Can you be an elite powerlifter and still play sports all week? Probably not but you can still put on some size and be plenty strong. PLENTY strong.