This Doesn't Seem Normal

My boyfriend was severely abused as a child. I always knew that, but tonight he was painting my nails and we were talking about clubs. I asked if he did any clubs in middle school and he said he has almost no memories before the of 15. I asked how and he just shrugged. He said he guess he brain doesn't want him to remember trauma. Is that even possible. To forget your whole childhood? I told him he should go to hypnotherapy to get his memories back but he's just said "I'm good". I can't imagine forgetting my whole childhood. I think him refusing to try to remember is super unhealthy! This doesn't seem normal!