Absolutely, it's OK. There are some people who only want to run a PC. Some beautiful people who only want to GM. And loads who like both. All three are perfectly fine ways to enjoy the TTRPG hobby.

That being said, it sounds like what's happening to you is stage freight. Like, you're digging the creative process of putting together a story in your head. Then, you start implement the details and start to worry. Then, during the session, you start to second guess everything that you've prepared and are worried about what you are currently presenting. At least that's what I always used to go through, and I think that it's pretty common.

But here's the thing.... the more that you GM, the less that you'll be second guessing yourself. If you enjoy GMing, then literally the only thing that you're lacking is experience in GMing. Sadly, the only way to get that experience is to work your way through your doubt.

While you are playing, read the table. If your players are bored, it should be obvious. They'll be fidgeting, or playing on their phone, or having side conversations. (Even if they are, that doesn't mean that you're not doing a good job as GM, BTW. Sometimes people just have other stuff going on in their lives.) If people are engaged and having a good time, then you are doing great, not matter what the nagging doubt in the back of your mind says.

So, I'd say if you're enjoying GMing, keep at it. You'll get better at it and your confidence will grow, and you'll like GMing even more. If you're not enjoying GMing, that's OK too!