Does anyone feel like an actual adult?

I don’t feel like an actual adult. I feel like I’m pretending to know what I’m doing.

That's the first step. The next step is looking back on your "mundane" adult accomplishments:

• Finding and negotiating your housing
• Making sure you (and possibly your family) are maintaining basic nutrition
• Managing your finances well enough that the first two are not in imminent danger
• Navigating though various "adult" BS such as contacting a bank or merchant about a process or payment in error, and chasing it through various channels until its resolved.
• Identifying your next need and the starting point for how to go about getting it resolved.

Then you glance to your left and your right and see some of your peers doing magically better, but more importantly you see a chunk of your peers not able to accomplish anything in the list above. You see what you now recognize is your growth and maturing and their lack of it.

The second step is to realize that you are indeed an adult. This is what being an adult is. The situations change, the difficulty in scope or scale increases, but its variations on what you've done before and the second, third, fourth...hundredth iteration aren't as hard as your first attempt in your early adulthood.

You realize that there isn't a single defining threshold you crossed at some point in the past where you went from "kid" to "adult". You also realize that some people make it all the way into their 60s and 70s without ever becoming an adult.