I was thinking about boundaries myself recently when I remembered my brother used to do the same thing you mention when I was a kid. He'd just walk into my room, sometimes knock and then push the door open. I have memories of pushing the door closed from inside my bedroom with him shoving his way in. Unbelievable really when I look back.

Just edited this reply as read your post properly... It does seem from my outsider's perspective that perhaps your mother's behaviour is contributing to your anxiety and panic. Constantly living with the fear of someone walking into our private safe place has got be really anxiety inducing. If you're managing anxiety having somewhere safe and private where you can regroup is essential.

It sounds like your Mum has issues of her own but you need to try and separate yours from hers. Hope you manage to get this sorted as sounds like it's really difficult for you and you're being guilt tripped and made to feel bad over what to most people would be a perfectly reasonable request for your right to set the most basic of boundaries.