In my experience, most people gradually grow into feeling like an adult. Living with your parents certainly doesn't "disqualify" you from being an adult, but I know it does make it harder to feel like one for most people.

When we are around our parents, most of us feel our "childhood role" pulling at us, and we feel less grown-up. For lots or even most of us, this problem can last well beyond our 20s.

So, if you want to feel more grown-up, it could be worth your time to explore options for living away from your parents. It will probably mean living in a much less nice situation. You have to decide if that's important enough to your psychological health to go for it. There are options like living in a group house that can be lots less expensive than renting your own apartment.

You sound like you need to get out on your own. I hope that you're able to do that. If it's just too expensive right now, how much longer are you looking at for grad school? Two years? Or are you talking about an advanced degree?

Another thing to consider is if you will have an office or shared area at the school when you become a grad student. Being in grad school can often give you a place to spend more time at school, so you're only at home for sleeping.