Buy good headgear, like $80-100 that Boxers use, and not the junk that many TMA schools train with, made by Century, Pro Force... You are taking a lot of risks at your age with head shots...sparring, even with the agreed upon, light level, can spike to hard at times when people get mad....but it's true, getting hit pretty hard and often, is apart of real Self Defense training.
I'll argue one adjustment to that: getting hit hard and often in the head is apart from Self Defense training. It delivers the exact things we're working to avoid: potential long-term injury. Taking an occasional reasonably hard shot to the head can help prepare mentally and emotionally. Getting hit more often than that, and with full force, is harmful even with head gear or boxing gloves.
It's a question of priorities. If I want to be the best I can possibly be, I should start training as early as I can, train as often as I can, and train as hard as I can. Then, for a while (until the injuries catch up, if I've received any), I'll be the best I can be. For most of us training for SD, we need to be reasonably prepared for the most likely and most common attacks, plus whatever preparedness we can gain for the less-likely ones.