Okay. As long as you have a trainer, you should be fine. The problem occurs when you start lifting so much weight that your core can't support it. It usually happens during power moves with free weights where a great deal of acceleration is used.
Try to be aware of any lower back pain that may occur and let your trainer know immediately if you experience it. You've gone through a lot of effort and I'd hate to see you benched by an injury.
You're only young once, but you can be immature forever.