LO Headbutting Everything

My 9 month old son head butts EVERYTHING. Doors he wants opened, his crib when he doesn't want to nap, windows, my head, he just always goes head first. I try to stop him but it doesn't seem to have any lasting affect. He's got bruises all along his forehead and it looks really bad, I'm worried people think I'm hurting him 😭. My MIL comments on every bruise "her baby" has and I feel like she's trying to make me feel like crap. Any helpful ways I can stop him or am I just going to have to let him outgrow it? Pics

shows some of his bruises

*Edit: I sent my MIL a picture of him and the first thing she says is what's with all the bruises 😧. I always keep an eye out when he's been hitting things for signs of concussion, and he seems ok and doesn't even act like it hurts. He has his 9 month appt on Jan 3rd right before he turns 10 months so I'll ask his ped about it if it's not gotten better by then. Thank you ladies for all the advice and experiences. I really hope it's nothing.