One year old harming himself

My one year old son has been harming himself for 9 months now. It started when he was 7 months old he would smack his head over and over. He does that less but now he bites himself, bashes his head in to the floors walls and doors repeatedly, & he smacks himself in the face repeatedly.

We’ve never used spanking for discipline so I’m not sure if it’s a learned behavior.

It scares me and breaks my heart to watch him hurt himself. He will do it until he is hurt and in tears. If I stop him he has a complete tantrum. He gets bruises on his forehead and I feel like an awful mother 🤦🏼‍♀️

I need tips and advice. Reassurance that it’s normal would be great too. It’s just been months. I thought it was cute at first and though it would be a phase but it just keeps getting worse.