that I'm not allowed to take any of my stuff.

Your clothes are yours. Your shoes are yours. Items given to you by them are yours. Things like cars or computers can be argued, but uniquely person items cannot.

Your size 14 (grand)mother is not going to fit in your size 6 jeans, so she is going to lose the argument that they are hers.

If they are your guardians, then they are required to provide you clothing. You are 18, so yea, they can legally kick you out if they want.

It's time to ensure that all of YOUR stuff is in your name.

If you have a vehicle, get it in your name. Some people in your situation pay their parents money for a vehicle that is "theirs" but it's never in their name. Even when they paid for it, the parents have threatened to take it back. If you have any of these type of arrangements, then get them in your name, or stop payment.

Come up with any reason you can think of.

"What if I get into an accident. I wouldn't want a vehicle in YOUR name to be attached to an accident. It's better for you legally if it's in my name if I drive it."

Whatever BS you can think of.

Separate yourself as much as possible from them as soon as you can. These situations will only get worse the older you get.

The more control you have over your life, the harder they will squeeze.