It took me a few months and I still hesitate when gendering myself sometimes, but it's hesitation now, not correction. It helps that I'm out full-time now, though and have been for over a month. You'll get there, girl. Just be kind to yourself.
It's been a year and I still deadname myself when I am frustrated. You'll get there! It was such a good moment for me when the gendered language flipped in my head and started saying some things "right"(like how I wanted to be a voice actress instead of a voice actor). You've been calling yourself a guy for as long as you can remember, and it's all new(ish)! Give yourself grace!