Can I Diet while pregnant?

Al

I’m 2 days before my missed period. I tested Monday and yesterday and got positives both times. I’m 320lbs, 23, and I’m freaking out! Literally no one knows because it’s so soon and I’m so paranoid about what I eat now. Can I lose weight while still having a healthy pregnancy? I’ve been drinking only water and counting calories since last week. Any advice is welcome. I’m an over thinker obviously 😂